Vertical Takeoff to a Hover part of the vertical thrust is diverted, resulting in a loss of
altitude. To maintain altitude, increase the collective. This
A vertical takeoff to a hover involves flying the helicopter increases drag on the blades and tends to slow them down. To
from the ground vertically to a skid height of two to three counteract the drag and maintain rpm, increase the throttle.
feet, while maintaining a constant heading. Once the desired Increased throttle means increased torque, so the pilot must
skid height is achieved, the helicopter should remain nearly add more pedal pressure to maintain the heading. This can
motionless over a reference point at a constant altitude and easily lead to overcontrolling the helicopter. However, as
on a constant heading. The maneuver requires a high degree level of proficiency increases, problems associated with
of concentration and coordination. overcontrolling decrease. Helicopter controls are usually
more driven by pressure than by gross control movements.
Technique
The pilot on the controls needs to clear the area left, right, Common Errors
and above to perform a vertical takeoff to a hover. The
pilot should remain focused outside the aircraft and obtain 1. Failing to ascend vertically as the helicopter becomes
clearance to take off from the controlling tower. If necessary, airborne.
the pilot who is not on the controls assists in clearing the
aircraft and provides adequate warning of any obstacles and 2. Pulling excessive collective to become airborne,
any unannounced or unusual drift/altitude changes. causing the helicopter to gain too much altitude.
Heading control, direction of turn, and rate of turn at hover 3. Overcontrolling the antitorque pedals, which not only
are all controlled by using the pedals. Hover height, rate of changes the heading of the helicopter, but also changes
ascent, and the rate of descent are controlled by using the the rpm.
collective. Helicopter position and the direction of travel are
controlled by the cyclic. 4. Reducing throttle rapidly in situations in which
proper rpm has been exceeded, usually resulting in
After receiving the proper clearance and ensuring that the exaggerated heading changes and loss of lift, resulting
area is clear of obstacles and traffic, begin the maneuver in loss of altitude.
with the collective in the down position and the cyclic in
a neutral position, or slightly into the wind. Very slowly 5. Failing to ascend slowly.
increase the collective until the helicopter becomes light
on the skids or wheels. At the same time apply pressure Hovering
and counter pressure on the pedals to ensure the heading
remains constant. Continue to apply pedals as necessary to Hovering is a maneuver in which the helicopter is maintained
maintain heading and coordinate the cyclic for a vertical in nearly motionless flight over a reference point at a constant
ascent. As the helicopter slowly leaves the ground, check altitude and on a constant heading.
for proper attitude control response and helicopter center of
gravity. A slow ascent will allow stopping if responses are Technique
outside the normal parameters indicating hung or entangled To maintain a hover over a point, use sideview and peripheral
landing gear, center of gravity problems, or control issues. vision to look for small changes in the helicopter’s attitude
If a roll or tilt begin, decrease the collective and determine and altitude. When these changes are noted, make the
the cause of the roll or tilt. Upon reaching the desired hover necessary control inputs before the helicopter starts to
altitude, adjust the flight controls as necessary to maintain move from the point. To detect small variations in altitude
position over the intended hover area. Student pilots should or position, the main area of visual attention needs to be
be reminded that while at a hover, the helicopter is rarely some distance from the aircraft, using various points on the
ever level. Helicopters usually hover left side low due to the helicopter or the tip-path plane as a reference. Looking too
tail rotor thrust being counteracted by the main rotor tilt. A closely or looking down leads to overcontrolling. Obviously,
nose low or high condition is generally caused by loading. in order to remain over a certain point, know where the point
Once stabilized, check the engine instruments and note the is, but do not focus all attention there.
power required to hover.
As with a takeoff, the pilot controls altitude with the collec
Excessive movement of any flight control requires a change tive and maintains a constant rpm with the throttle. The cyclic
in the other flight controls. For example, if the helicopter is used to maintain the helicopter’s position; the pedals, to
drifts to one side while hovering, the pilot naturally moves control heading. To maintain the helicopter in a stabilized
the cyclic in the opposite direction. When this is done, hover, make small, smooth, coordinated corrections. As the
desired effect occurs, remove the correction in order to stop the
helicopter’s movement. For example, if the helicopter begins
to move rearward, apply a small amount of forward cyclic
9-3
pressure. However, neutralize this pressure just before the As the turn begins, use the cyclic as necessary (usually into
helicopter comes to a stop, or it will begin to move forward. the wind) to keep the helicopter over the desired spot. To
continue the turn, add more pedal pressure as the helicopter
After experience is gained, a pilot develops a certain “feel” turns to the crosswind position. This is because the wind is
for the helicopter. Small deviations can be felt and seen, striking the tail surface and tail rotor area, making it more
so you can make the corrections before the helicopter difficult for the tail to turn into the wind. As pedal pressures
actually moves. A certain relaxed looseness develops, and increase due to crosswind forces, increase the cyclic pressure
controlling the helicopter becomes second nature, rather than into the wind to maintain position. Use the collective with the
a mechanical response. throttle to maintain a constant altitude and rpm. [Figure 9-1]
Common Errors After the 90° portion of the turn, decrease pedal pressure
slightly to maintain the same rate of turn. Approaching the
1. Tenseness and slow reactions to movements of the 180°, or downwind portion, anticipate opposite pedal pressure
helicopter. due to the tail moving from an upwind position to a down
wind position. At this point, the rate of turn has a tend ency
2. Failure to allow for lag in cyclic and collective pitch, to increase at a rapid rate due to the tendency of the tail
which leads to overcontrolling. It is very common for surfaces to weathervane. Because of the tailwind condition,
a student to get ahead of the helicopter. Due to inertia, hold rearward cyclic pressure to keep the helicopter over
it requires some small time period for the helicopter the same spot.
to respond.
The horizontal stabilizer has a tendency to lift the tail during
3. Confusing attitude changes for altitude changes, which a tailwind condition. This is the most difficult portion of
results in improper use of the controls. the hovering turn. Horizontal and vertical stabilizers have
several different designs and locations, including the canted
4. Hovering too high, creating a hazardous flight stabilizers used on some Hughes and Schweizer helicopters.
condition. The height velocity chart should be The primary purpose of the vertical stabilizer is to unload
referenced to determine the maximum skid height the work of the antitorque system and to aid in trimming the
to hover and safely recover the helicopter should a helicopter in flight should the antitorque system fail. The
malfunction occur. horizontal stabilizer provides for a more usable CG range
and aids in trimming the helicopter longitudinally.
5. Hovering too low, resulting in occasional touchdown.
Because of the helicopter’s tendency to weathervane,
6. Becoming overly confident over prepared surfaces maintaining the same rate of turn from the 180° position
when taking off to a hover. Be aware that dynamic actually requires some pedal pressure opposite the direction
rollover accidents usually occur over a level surface. of turn. If a pilot does not apply opposite pedal pressure,
the helicopter tends to turn at a faster rate. The amount of
Hovering Turn pedal pressure and cyclic deflection throughout the turn
depends on the wind velocity. As the turn is finished on the
A hovering turn is a maneuver performed at hovering altitude upwind heading, apply opposite pedal pressure to stop the
in which the nose of the helicopter is rotated either left or turn. Gradually apply forward cyclic pressure to keep the
right while maintaining position over a reference point on the helicopter from drifting.
surface. Hovering turns can also be made around the mast or
tail of the aircraft. The maneuver requires the coordination Control pressures and direction of application change
of all flight controls and demands precise control near the continuously throughout the turn. The most dramatic change
surface. A pilot should maintain a constant altitude, rate of is the pedal pressure (and corresponding power requirement)
turn, and rpm. necessary to control the rate of turn as the helicopter moves
through the downwind portion of the maneuver.
Technique
Initiate the turn in either direction by applying anti-torque
pedal pressure toward the desired direction. It should be noted
that during a turn to the left, more power is required because
left pedal pressure increases the pitch angle of the tail rotor,
which, in turn, requires additional power from the engine. A
turn to the right requires less power. (On helicopters with a
clockwise rotating main rotor, right pedal increases the pitch
angle and, therefore, requires more power.)
9-4
Cyclic—Forward Cyclic—Right Cyclic—Rearward Cyclic—Left Cyclic—Forward
WIND
WIND
Pedal Pedal Pedal Pedal Pedal
Some left in hover, more Most left pressure in Changing from left to Most right pedal Some right to stop turn,
left to start turn to left turn right pressure pressure in turn then left to maintain
heading
Collective Collective Collective Collective Collective
Adjust collective as Adjust collective as Adjust collective as Adjust collective as Adjust collective as
necessary to maintain necessary to maintain necessary to maintain necessary to maintain necessary to maintain
proper hover height proper hover height proper hover height proper hover height proper hover height
Throttle Throttle Throttle Throttle Throttle
As necessary to As necessary to As necessary to As necessary to As necessary to
maintain rpm maintain rpm maintain rpm maintain rpm maintain rpm
Normally left pedal Normally left pedal Normally left pedal Normally left pedal
application requires application requires application requires application requires
more throttle more throttle more throttle more throttle
Figure 9-1. Left turns in helicopters with a counterclockwise rotating main rotor are more difficult to execute because the tail rotor
demands more power. This requires you to compensate with additional left pedal and increased throttle. Refer to this graphic throughout
the remainder of the discussion on a hovering turn to the left.
Turns can be made in either direction; however, in a high Hovering—Forward Flight
wind condition, the tail rotor may not be able to produce
enough thrust, which means the pilot cannot control a turn Forward hovering flight is normally used to move a helicopter
to the right in a counterclockwise rotor system. Therefore, to a specific location, and it may begin from a stationary
if control is ever questionable, first attempt to make a 90° hover. During the maneuver, constant groundspeed, altitude,
turn to the left. If sufficient tail rotor thrust exists to turn and heading should be maintained.
the helicopter crosswind in a left turn, a right turn can be
successfully controlled. The opposite applies to helicopters Technique
with clockwise rotor systems. In this case, start the turn to Before starting, pick out two references directly in front and
the right. Hovering turns should be avoided in winds strong in line with the helicopter. These reference points should be
enough to preclude sufficient aft cyclic control to maintain kept in line throughout the maneuver. [Figure 9-2]
the helicopter on the selected surface reference point
when headed downwind. Check the flight manual for the
manufacturer’s recomm endations for this limitation.
Common Errors Reference point
1. Failing to maintain a slow, constant rate of turn.
2. Failing to maintain position over the reference point. A OM
3. Failing to maintain rpm within normal range.
4. Failing to maintain constant altitude. CLUTCH MR MR STARTER TR lOW LOW
5. Failing to use the antitorque pedals properly. TEMP CHIP ON CHIP FUEL RPM
ER 0 6 E1
33 3
KNOTS 20 30 10 9 0 II00 FEET
110 110 100 120 20 30 40 40 20 20 8 2
100 100 50 I0 I0 7 3322099...098
90 90 90 110 MPH CALIBRATED ALT
I0 I0 TO
80 80 100 20 20
70 70 20,000 FEET
60
50 60 90 60 50
50 80 70
80 60 654
%RPM 70 STBY PWR TEST
15 20 25 LR 24 30 5 I0 15
MANFOLD 2 MIN TURN UP VERTICAL SPEED
I5 2I 0 20100 FEET PER MINUTE
10 PRESS 30 DC ELEC W 30
5 35IN Hg 6 I2 DOWN I0 15
5
ALg.
33 N 3
GS
Figure 9-2. To maintain a straight ground track, use two reference
points in line and at some distance in front of the helicopter.
9-5
Begin the maneuver from a normal hovering altitude by
applying forward pressure on the cyclic. As movement
begins, return the cyclic toward the neutral position to
maintain low groundspeed—no faster than a brisk walk.
Throughout the maneuver, maintain a constant groundspeed
and path over the ground with the cyclic, a constant heading
with the antitorque pedals, altitude with the collective, and
the proper rpm with the throttle.
To stop the forward movement, apply rearward cyclic Reference point
pressure until the helicopter stops. As forward motion stops,
return the cyclic to the neutral position to prev ent rearward
movement. Forward movement can also be stopped by
simply applying rearward pressure to level the helicopter
and allowing it to drift to a stop.
Common Errors Figure 9-3. The key to hovering sideward is establishing at least
two reference points that help maintain a straight track over the
1. Exaggerated movement of the cyclic, resulting in ground while keeping a constant heading.
erratic movement over the surface.
rpm. Be aware that the nose tends to weathervane into the
2. Failure to use proper antitorque pedal control, resulting wind. Changes in the pedal position will change the rpm
in excessive heading change. and must be corrected by collective and/or throttle changes
to maintain altitude.
3. Failure to maintain desired hovering altitude.
4. Failure to maintain proper rpm.
5. Failure to maintain alignment with direction of travel.
Hovering—Sideward Flight To stop the sideward movement, apply cyclic pressure in
the direction opposite to that of movement and hold it until
Sideward hovering flight may be necessary to move the the helicopter stops. As motion stops, return the cyclic to
helicopter to a specific area when conditions make it the neutral position to prevent movement in the opposite
impossible to use forward flight. During the maneuv er, direction. Applying sufficient opposite cyclic pressure to
a constant groundspeed, altitude, and heading should be level the helicopter may also stop sideward movement. The
maintained. helicopter then drifts to a stop.
Technique Common Errors
Before starting sideward hovering flight, ensure the area
for the hover is clear, especially at the tail rotor. Constantly 1. Exaggerated movement of the cyclic, resulting in
monitor hover height and tail rotor clearance during all overcontrolling and erratic movement over the surface.
hovering maneuvers to prevent dynamic rollover or tail
rotor strikes to the ground. Then, pick two points of in-line 2. Failure to use proper antitorque pedal control, resulting
reference in the direction of sideward hovering flight to help in excessive heading change.
maintain the proper ground track. These reference points
should be kept in line throughout the maneuver. [Figure 9-3] 3. Failure to maintain desired hovering altitude.
Begin the maneuver from a normal hovering altitude by 4. Failure to maintain proper rpm.
applying cyclic toward the side in which the movement is
desired. As the movement begins, return the cyclic toward the 5. Failure to make sure the area is clear prior to starting
neutral position to maintain low groundspeed—no faster than the maneuver.
a brisk walk. Throughout the maneuver, maintain a constant
groundspeed and ground track with cyclic. Maintain heading, Hovering—Rearward Flight
which in this maneuver is perpendicular to the ground track,
with the antitorque pedals, and a constant altitude with the Rearward hovering flight may be necessary to move the
collective. Use the throttle to maintain the proper operating helicopter to a specific area when the situation is such that
forward or sideward hovering flight cannot be used. During
the maneuver, maintain a constant groundspeed, altitude, and
heading. Due to the limited visibility behind a helicopter, it
9-6
is important that the area behind the helicopter be cleared Hover taxi (25 feet or less)
before beginning the maneuver. Use of ground personnel is
recommended.
Technique
Before starting rearward hovering flight, pick out two
reference points in front of, and in line with the helicopter
just like hovering forw ard. [Figure 9-2] The movement of
the helicopter should be such that these points remain in line.
Begin the maneuver from a normal hovering altitude Poor surface conditions or skid type helicopters
by applying rearward pressure on the cyclic. After the
movement has begun, position the cyclic to maintain a slow Figure 9-4. Hover taxi.
groundspeed—no faster than a brisk walk. Throughout the
maneuver, maintain constant groundspeed and ground track Air Taxi
with the cyclic, a constant heading with the antitorque pedals, An air taxi is preferred when movements require greater
constant altitude with the collective, and the proper rpm with distances within an airport or heliport boundary. [Figure 9-5]
the throttle. In this case, fly to the new location; however, it is expected
that the helicopter will remain below 100 feet AGL with
To stop the rearward movement, apply forward cyclic and an appropriate airspeed and will avoid over flight of other
hold it until the helicopter stops. As the motion stops, return aircraft, vehicles, and personnel.
the cyclic to the neutral position. Also, as in the case of
forward and sideward hovering flight, opposite cyclic can Air taxi (100 feet or less)
be used to level the helicopter and let it drift to a stop. Tail
rotor clearance must be maintained. Generally, a higher-than-
normal hover altitude is preferred.
Common Errors Faster travel
1. Exaggerated movement of the cyclic resulting in Figure 9-5. Air taxi.
overcontrolling and an uneven movement over the
surface. Technique
Before starting, determine the appropriate airspeed and
2. Failure to use proper antitorque pedal control, resulting altitude combination to remain out of the cross-hatched or
in excessive heading change. shaded areas of the height-velocity diagram. Additionally, be
aware of crosswind conditions that could lead to loss of tail
3. Failure to maintain desired hovering altitude. rotor effectiveness. Pick out two references directly in front
of the helicopter for the ground path desired. These reference
4. Failure to maintain proper rpm. points should be kept in line throughout the maneuver.
5. Failure to make sure the area is clear prior to starting
the maneuver.
Taxiing
Taxiing refers to operations on or near the surface of taxiways
or other prescribed routes. Helicopters utilize three different
types of taxiing.
Hover Taxi Begin the maneuver from a normal hovering altitude by
A hover taxi is used when operating below 25 feet above applying forward pressure on the cyclic. As movem ent
ground level (AGL). [Figure 9-4] Since hover taxi is just like begins, attain the desired airspeed with the cyclic. Control the
forward, sideward, or rearward hovering flight, the technique desired altitude with the collective and rpm with the throttle.
to perform it is not presented here. Throughout the maneuver, maintain a desired groundspeed
9-7
and ground track with the cyclic, a constant heading with Technique
antitorque pedals, the desired altitude with the collective, The helicopter should be in a stationary position on the surface
and proper operating rpm with the throttle. with the collective full down and the rpm the same as that
used for a hover. This rpm should be maintained throughout
To stop the forward movement, apply aft cyclic pressure to the maneuver. Then, move the cyclic slightly forward and
reduce forward speed. Simultaneously lower the collective to apply gradual upward press ure on the collective to move
initiate a descent to hover altitude. As forward motion stops, the helicopter forward along the surface. Use the antitorque
return the cyclic to the neutral position to prevent rearward pedals to maintain heading and the cyclic to maintain ground
movement. As approaching the proper hover altitude, track. The collective controls starting, stopping, and speed
increase the collective as necessary to stop descent at hover while taxiing. The higher the collective pitch, the faster the
altitude (much like a quick stop maneuver). taxi speed; however, do not taxi faster than a brisk walk. If
the helicopter is equipped with brakes, use them to help slow
Common Errors down. Do not use the cyclic to control groundspeed.
1. Erratic movement of the cyclic, resulting in improper During a crosswind taxi, hold the cyclic into the wind a
airspeed control and erratic movement over the surface. sufficient amount to eliminate any drifting movement.
2. Failure to use proper antitorque pedal control, resulting Common Errors
in excessive heading change.
1. Improper use of cyclic.
3. Failure to maintain desired altitude.
2. Failure to use antitorque pedals for heading control.
4. Failure to maintain proper rpm.
3. Improper use of the controls during crosswind
5. Overflying parked aircraft causing possible damage operations.
from rotor downwash.
4. Failure to maintain proper rpm.
6. Flying in the cross-hatched or shaded area of the
height-velocity diagram. Normal Takeoff From a Hover
7. Flying in a crosswind that could lead to loss of tail A normal takeoff from a hover is an orderly transition to
rotor effectiveness. forward flight and is executed to increase altitude safely and
expeditiously. During the takeoff, fly a profile that avoids the
8. Excessive tail-low attitudes. cross-hatched or shaded areas of the height-velocity diagram.
9. Excessive power used or required to stop. Technique
Refer to Figure 9-7 (position 1). Bring the helicopter to a
10. Failure to maintain alignment with direction of travel. hover and make a performance check, which includes power,
balance, and flight controls. The power check should include
Surface Taxi an evaluation of the amount of excess power available; that
A surface taxi is used to minimize the effects of rotor is, the difference between the power being used to hover and
downwash. [Figure 9-6] Avoid excessive cyclic displacement the power available at the existing altitude and temperature
while surface taxiing or on the ground which can lead to main conditions. The balance condition of the helicopter is
rotor blades contacting the helicopter or rotor mast. This indicated by the position of the cyclic when maintaining a
technique may be used with wheeled aircraft, or with those stationary hover. Wind necessitates some cyclic deflection,
that have floats, skids or skis. but there should not be an extreme deviation from neutral.
Flight controls must move freely, and the helicopter should
Surface taxi respond normally. Then, visually clear the surrounding area.
Less rotor downwash Start the helicopter moving by smoothly and slowly easing the
Figure 9-6. Surface taxi. cyclic forward (position 2). As the helicopter starts to move
forward, increase the collective, as necessary, to prevent the
helicopter from sinking and adjust the throttle to maintain
rpm. The increase in power requires an increase in the proper
antitorque pedal to maintain heading. Maintain a straight
takeoff path throughout the takeoff.
9-8
5
4
3
12
Figure 9-7. The helicopter takes several positions during a normal takeoff from hover.
While accelerating through effective translational lift (position Normal Takeoff From the Surface
3), the helicopter begins to climb and the nose tends to rise
due to increased lift. At this point, adjust the collective to Normal takeoff from the surface is used to move the helicopter
obtain normal climb power and apply enough forward cyclic from a position on the surface into effective translational lift
to overcome the tendency of the nose to rise. At position 4, and a normal climb using a minimum amount of power. If the
hold an attitude that allows a smooth acceleration toward surface is dusty or covered with loose snow, this technique
climbing airspeed and a commensurate gain in altitude so that provides the most favorable visibility conditions and reduces
the takeoff profile does not take the helicopter through any the possibility of debris being ingested by the engine.
of the cross-hatched or shaded areas of the height-velocity
diagram. As airspeed increases (position 5), place the aircraft Technique
in trim and allow a crab to take place to maintain ground track Place the helicopter in a stationary position on the surface.
and a more favorable climb configuration. As the helicopter Lower the collective to the full down position, and reduce
continues to climb and accelerate to best rate-of-climb, apply the rpm below operating rpm. Visually clear the area and
aft cyclic pressure to raise the nose smoothly to the normal select terrain features or other objects to aid in maintaining
climb attitude. the desired track during takeoff and climb out. Increase the
throttle to the proper rpm, and raise the collective slowly
Common Errors until the helicopter is light on the skids. Hesitate momentarily
and adjust the cyclic and antitorque pedals, as necessary, to
1. Failing to use sufficient collective pitch to prevent loss prevent any surface movement. Continue to apply upward
of altitude prior to attaining translational lift. collective. As the helicopter leaves the ground, use the cyclic,
as necessary, to begin forward movement as altitude is
2. Adding power too rapidly at the beginning of the gained. Continue to accelera te, and as effective translational
transition from hovering to forward flight without lift is attained, the helicopter begins to climb. Adjust attitude
forward cyclic compensation, causing the helicopter and power, if necessary, to climb in the same manner as a
to gain excessive altitude before acquiring airspeed. takeoff from a hover. A second less efficient but acceptable
technique is to attempt a vertical takeoff to evaluate if power
3. Assuming an extreme nose-down attitude near the or lift is sufficient to clear obstructions. This allows the
surface in the transition from hovering to forward helicopter to be returned to the takeoff position if required.
flight.
Common Errors
4. Failing to maintain a straight flightpath over the
surface (ground track).
5. Failing to maintain proper airspeed during the climb. 1. Departing the surface in an attitude that is too nose-
low. This situation requires the use of excess ive power
6. Failing to adjust the throttle to maintain proper rpm. to initiate a climb.
7. Failing to transition to a level crab to maintain ground
track.
9-9
2. Using excessive power combined with a level attitude, Ground Track Wind Movement
which causes a vertical climb, unless needed for Helicopter Heading
obstructions and landing considerations.
3. Application of the collective that is too abrupt when
departing the surface, causing rpm and heading control
errors.
Crosswind Considerations During
Takeoffs
If the takeoff is made during crosswind conditions, the
helicopter is flown in a slip during the early stages of the
maneuver. [Figure 9-8] The cyclic is held into the wind a
sufficient amount to maintain the desired ground track for
the takeoff. The heading is maintained with the use of the
antitorque pedals. In other words, the rotor is tilted into the
wind so that the sideward movement of the helicopter is
just enough to counteract the crosswind effect. To prevent
the nose from turning in the direction of the rotor tilt, it is
necessary to increase the antitorque pedal pressure on the
side opposite the cyclic.
Helicopter Wind movement Figure 9-9. To compensate for wind drift at altitude, crab the
side movement helicopter into the wind.
Figure 9-8. During a slip, the rotor disk is tilted into the wind. component from the main rotor. By doing this, it causes the
nose of the helicopter to lower which in turn will cause the
After approximately 50 feet of altitude is gained, make a airspeed to increase. In order to counteract this, the pilot
coordinated turn into the wind to maintain the desired ground must find the correct power setting to maintain level flight
track. This is called crabbing into the wind. The stronger by adjusting the collective. [Figure 9-10] The horizontal
the crosswind, the more the helicopter has to be turned into stabilizer aids in trimming the helicopter longitudinally and
the wind to maintain the desired ground track. [Figure 9-9] reduces the amount of nose tuck that would occur. On several
helicopters, it is designed as a negative lift airfoil, which
Straight-and-Level Flight produces a lifting force in a downward direction.
Straight-and-level flight is flight in which constant altitude A OM
and heading are maintained. The attitude of the rotor disk
relative to the horizon determines the airspeed. The horizontal CLUTCH MR MR STARTER TR lOW LOW
stabilizer design determines the helicopter’s attitude when TEMP CHIP ON CHIP FUEL RPM
stabilized at an airspeed and altitude. Altitude is primarily
controlled by use of the collective. ER 0 6 E1
33 3
Technique KNOTS 20 30 10 9 0 II00 FEET
To maintain forward flight, the rotor tip-path plane must
be tilted forward to obtain the necessary horizontal thrust 110 110 100 120 20 30 40 40 20 20 8 2
100 100 50 I0 I0 7 3322099...098
90 90 90 110 MPH CALIBRATED ALT
I0 I0 TO
80 80 100 20 20
70 70 20,000 FEET
60
50 60 90 60 50
50 80 70
80 60 654
%RPM 70 STBY PWR TEST
15 20 25 LR 24 30 5 I0 15
MANFOLD 2 MIN TURN UP VERTICAL SPEED
I5 2I 0 20100 FEET PER MINUTE
10 PRESS 30 DC ELEC W 30
5 35IN Hg 6 I2 DOWN I0 15
5
ALg.
33 N 3
GS
Figure 9-10. Maintain straight-and-level flight by adjusting the rotor
tip-path plane forward but adjusting the collective as necessary to
maintain a constant airspeed and altitude. The natural horizon line
can be used as an aid in maintaining straight-and-level flight. If
the horizon line begins to rise, slight power may be required or the
nose of the helicopter may be too low. If the horizon line is slowly
dropping, some power may need to be taken out or the nose of the
helicopter may be too high, requiring a cyclic adjustment.
9-10
When in straight-and-level flight, any increase in the collective, flight, apply sideward pressure on the cyclic in the direction
while holding airspeed constant, causes the helicopter to climb. the turn is to be made. This is the only control movement
A decrease in the collective, while holding airspeed constant, needed to start the turn. Do not use the pedals to assist the
causes the helicopter to descend. A change in the collective turn. Use the pedals only to compensate for torque to keep
requires a coordinated change of the throttle to maintain a the helicopter in trim around the vertical axis. [Figure 9-11]
constant rpm. Additionally, the antitorque pedals need to keep Keeping the fuselage in the correct streamlined position
the helicopter in trim around the vertical axis. around the vertical axis facilitates the helicopter flying
forward with the least drag. Trim is indicated by a yaw string
To increase airspeed in straight-and-level flight, apply in the center, or a centered ball on a turn and slip indicator.
forward pressure on the cyclic and raise the collective as
necessary to maintain altitude. To decrease airspeed, apply
rearward pressure on the cyclic and lower the collective, as
necessary, to maintain altitude.
Although the cyclic is sensitive, there is a slight delay in Inertia
control reaction, and it is necessary to anticip ate actual
movement of the helicopter. When making cyclic inputs to HCL
control the altitude or airspeed of a helicopter, take care not
to overcontrol. If the nose of the helicopter rises above the Figure 9-11. During a level, coordinated turn, the rate of turn
level-flight attitude, apply forward pressure to the cyclic to is commensurate with the angle of bank used, and inertia and
bring the nose down. If this correction is held too long, the horizontal component of lift (HCL) are equal.
nose drops too low. Since the helicopter continues to change
attitude momentarily after the controls reach neutral, return
the cyclic to neutral slightly before the desired attitude is
reached. This principle holds true for any cyclic input.
Since helicopters are not very stable, but are inherently very How fast the helicopter banks depends on how much lateral
controllable, if a gust or turbulence causes the nose to drop, cyclic pressure is applied. How far the helicopter banks (the
the nose tends to continue to drop instead of returning to a steepness of the bank) depends on how long the cyclic is
straight-and-level attitude as it would on a fixed-wing aircraft. displaced. After establishing the proper bank angle, return
Therefore, a pilot must remain alert and fly the helicopter the cyclic toward the neutral position. When the bank is
at all times. established, returning the cyclic to neutral or holding it
inclined relative to the horizon will maintain the helicopter
Common Errors at that bank angle. Increase the collective and throttle to
maintain altitude and rpm. As the torque increases, increase
1. Failure to trim the helicopter properly, tending to hold the proper antitorque pedal pressure to maintain longitudinal
antitorque pedal pressure and opposite cyclic. This is trim. Depending on the degree of bank, additional forward
commonly called cross-controlling. cyclic pressure may be required to maintain airspeed.
2. Failure to maintain desired airspeed. Rolling out of the turn to straight-and-level flight is the same
as the entry into the turn except that pressure on the cyclic
3. Failure to hold proper control position to maintain is applied in the opposite direction. Since the helicopter
desired ground track. continues to turn as long as there is any bank, start the rollout
before reaching the desired heading.
4. Failure to allow helicopter to stabilize at new airspeed.
The discussion on level turns is equally applicable to making
Turns turns while climbing or descending. The only difference is
that the helicopter is in a climbing or descending attitude
A turn is a maneuver used to change the heading of the rather than that of level flight. If a simultaneous entry is
helicopter. The aerodynamics of a turn were previously desired, merely combine the techniques of both maneuvers—
discussed in Chapter 3, Aerodynamics of Flight. climb or descent entry and turn entry. When recovering
from a climbing or descending turn, the desired heading and
Technique altitude are rarely reached at the same time. If the heading is
Before beginning any turn, the area in the direction of the
turn must be cleared not only at the helicopter’s altitude, but
also above and below. To enter a turn from straight-and-level
9-11
reached first, stop the turn and maintain the climb or descent Skid
until reaching the desired altitude. On the other hand, if the
altitude is reached first, establish the level flight attitude and
continue the turn to the desired heading.
Slips HCL
A slip occurs when the helicopter slides sideways toward
the center of the turn. [Figure 9-12] It is caused by an Inertia
insufficient amount of antitorque pedal in the direction of
the turn, or too much in the direction opposite the turn, in Figure 9-13. During a skid, the rate of turn is too great for the
relation to the amount of power used. In other words, if you angle of bank used, and inertia exceeds the horizontal component
hold improper antitorque pedal press ure, which keeps the of lift (HCL).
nose from following the turn, the helicopter slips sideways
toward the center of the turn. Slip
Slip
HCL
Inertia 46 LTO 6 100
4 100
Acceleration knots SA 8 100 40 160 60
G UNITS 80
2 8 2 10 knots
90 140
0 winter knots
0 10 50 50 50 2 10 120 100 80
PUSH -4 4 68
-2 20
60
70
OFF GO 9 0 II00 FEET FOR
AVG N 30 60 E 120 150
NET FNCN
+ STEER
PULL L VOL BATT 2ALT 2299..98
NAV PWR 330.0 FOR
− 8 S 210 240 W 300 330
DIST KNOTS 7 CALIBRATED
PUSH ALT SEL TO STEER
ON ON
HW 20,000 FEET
RADIO
PUSH 6 54
Figure 9-12. During a slip, the rate of turn is too low for the angle Coordinated
of bank used, and the horizontal component of lift (HCL) exceeds
inertia. 46 LTO 6
4
Skids Acceleration knots SA 8 40 160 60
A skid occurs when the helicopter slides sideways away from G UNITS 80
the center of the turn. [Figure 9-13] It is caused by too much 2 8 2 10 knots
antitorque pedal pressure in the direction of the turn, or by 90 140
too little in the direction opposite the turn in relation to the 0 winter knots
amount of power used. If the helicopter is forced to turn faster
with increased pedal pressure instead of by increasing the 0 10 2 10 120 100 80
degree of the bank, it skids sideways away from the center PUSH -4 4 68
of the turn instead of flying in its normal curved path. -2 20
In summary, a skid occurs when the rate of turn is too great 60
for the amount of bank being used, and a slip occurs when 70
the rate of turn is too low for the amount of bank being used.
[Figure 9-14] OFF GO 9 0 II00 FEET FOR
AVG N 30 60 E 120 150
NET FNCN
+ STEER
PULL L VOL BATT 2ALT 2299..98
NAV PWR 330.0 FOR
− 8 S 210 240 W 300 330
DIST KNOTS CALIBRATED
PUSH ALT SEL TO STEER
20,000 FEET ON ON
HW
7 RADIO
6 54
PUSH
Skid
46 LTO 6
4
Acceleration knots SA 8 60
2 G UNITS 8 802 10 40 160
900 winterknots knots
140
0 -2 10 2 10
PUSH -4 4 68 120 100 80
20
60
70
OFF GO 9 0 II00 FEET FOR
AVG N 30 60 E 120 150
NET FNCN
+ STEER
PULL L VOL BATT 2ALT 2299..98
NAV PWR 330.0 FOR
− 8 S 210 240 W 300 330
DIST KNOTS 7 CALIBRATED
PUSH ALT SEL TO STEER
ON ON
HW 20,000 FEET
RADIO
PUSH 6 54
Figure 9-14. Cockpit view of a slip and skid.
9-12
Normal Climb Normal Descent
The entry into a climb from a hover has already been described A normal descent is a maneuver in which the helicopter loses
in the Normal Takeoff from a Hover subsection; therefore, altitude at a controlled rate in a controlled attitude.
this discussion is limited to a climb entry from cruising flight.
Technique
Technique To establish a normal descent from straight-and-level flight
To enter a climb in a helicopter while maintaining airspeed, at cruising airspeed, lower the collective to obtain proper
the first actions are increasing the collective and throttle, power, adjust the throttle to maintain rpm, and increase
and adjusting the pedals as necessary to maintain a centered right antitorque pedal pressure to maintain heading in a
ball in the slip/skid indicator. Moving the collective up counterclockwise rotor system, or left pedal pressure in
requires a slight aft movement of the cyclic to direct all a clockwise system. If cruising airspeed is the same as or
of the increased power into lift and maintain the airspeed. slightly above descending airspeed, simultaneously apply
Remember, a helicopter can climb with the nose down and the necessary cyclic pressure to obtain the approximate
descend with the nose up. Helicopter attitude changes mainly descending attitude. If the pilot wants to decelerate, the
reflect acceleration or deceleration, not climb or descent. cyclic must be moved aft. If the pilot desires to descend
Therefore, the climb attitude is approximately the same as with increased airspeed, then forward cyclic is all that is
level flight in a stable climb, depending on the aircraft’s required if airspeed remains under the limit. As the helicopter
horizontal stabilizer design. stabilizes at any forward airspeed, the fuselage attitude will
streamline due to the airflow over the horizontal stabilizer. As
If the pilot wishes to climb faster, with a decreased airspeed, the airspeed changes, the airflow over the vertical stabilizer
then the climb can be initiated with aft cyclic. Depending or fin changes, so the pedals must be adjusted for trim.
on initial or entry airspeed for the climb, the climb can be
accomplished without increasing the collective, if a much The pilot should always remember that the total lift and thrust
slower airspeed is acceptable. However, as the airspeed vectoring is controlled by the cyclic. If a certain airspeed
decreases, the airflow over the vertical fin decreases is desired, it will require a certain amount of cyclic and
necessitating more antitorque (left) pedal application. collective movement for level flight. If the cyclic is moved,
the thrust-versus-lift ration is changed. Aft cyclic directs
To level off from a climb, start adjusting the attitude to the more power to lift, and altitude increases. Forward cyclic
level flight attitude a few feet prior to reaching the desired directs more power to thrust, and airspeed increases. If the
altitude. The amount of lead depends on the rate of climb at collective is not changed and there is a change only in cyclic,
the time of level-off (the higher the rate of climb, the more the total thrust to lift ration does not change; aft cyclic results
the lead). Generally, the lead is 10 percent of the climb rate. in a climb, and forward cyclic results in a descent with the
For example, if the climb rate is 500 feet per minute (fpm), corresponding airspeed changes.
you should lead the level-off by 50 feet.
To level off from the descent, lead the desired altitude by
To begin the level-off, apply forward cyclic to adjust and approximately 10 percent of the rate of descent. For examp le,
maintain a level flight attitude, which can be slightly nose a 500 fpm rate of descent would require a 50 foot lead. At
low. Maintain climb power until the airspeed approaches the this point, increase the collective to obtain cruising power,
desired cruising airspeed, then lower the collective to obtain adjust the throttle to maintain rpm, and increase left antitorque
cruising power and adjust the throttle to obtain and maintain pedal pressure to maintain heading (right pedal pressure in a
cruising rpm. Throughout the level-off, maintain longitudinal clockwise rotor system). Adjust the cyclic to obtain cruising
trim with the antitorque pedals. airspeed and a level flight attitude as the desired altitude is
reached.
Common Errors
Common Errors
1. Failure to maintain proper power and airspeed.
1. Failure to maintain constant angle of decent during
2. Holding too much or too little antitorque pedal. training.
3. In the level-off, decreasing power before adjusting the
nose to cruising attitude.
9-13
2. Failure to level-off the aircraft sufficiently, which usable reference points to start and complete the turns. In
results in recovery below the desired altitude. addition, the closer the track of the helicopter is to the field
boundaries, the steeper the bank necessary at the turning
3. Failure to adjust antitorque pedal pressures for changes points. The edges of the selected field should be seen while
in power. seated in a normal position and looking out the side of the
helicopter during either a left-hand or right-hand course. The
Ground Reference Maneuvers distance of the ground track from the edges of the field should
be the same regardless of whether the course is flown to the
Ground reference maneuvers may be used as training left or right. All turns should be started when the helicopter is
exercises to help develop a division of attention between abeam the corners of the field boundaries. The bank normally
the flightpath and ground references, and while controlling should not exceed 30°–45° in light winds. Strong winds may
the helicopter and watching for other airc raft in the vicinity. require more bank.
Other examples of ground reference maneuvers are flights
for photographic or observation purposes, such as pipe line The pilot should understand that when trying to fly a straight
or power line checks. Prior to each maneuver, a clearing line and maintain a specific heading, aircraft heading must be
turn should be accomplished to ensure the area is free of adjusted in order to compensate for the winds and stay on the
conflicting traffic. proper ground track. Also, keep in mind that a constant scan
of flight instruments and outside references aid in maintaining
Rectangular Course proper ground track.
The rectangular course is a training maneuver in which the
ground track of the helicopter is equidistant from all sides of a Although the rectangular course may be entered from any
selected rectangular area on the ground. While performing the direction, this discussion assumes entry on a downwind
maneuver, the altitude and airspeed should be held constant. heading. [Figure 9-15] while approaching the field boundary
The rectangular course helps develop recognition of a drift on the downwind leg, begin planning for an upcoming turn.
toward or away from a line parallel to the intended ground Since there is a tailwind on the downwind leg, the helicopter’s
track. This is helpful in recognizing drift toward or from an groundspeed is increased (position 1). During the turn, the
airport runway during the various legs of the airport traffic wind causes the helicopter to drift away from the field. To
pattern, and is also useful in observation and photographic counteract this effect, the roll-in should be made at a fairly
flights. fast rate with a relatively steep bank (position 2). This is
normally the steepest turn of the maneuver.
Technique
Maintaining ground track while trying to fly a straight line As the turn progresses, the tailwind component decreases,
can be very difficult for new pilots to do. It is important to which decreases the groundspeed. Consequently, the bank
understand the effects of the wind and how to compensate angle and rate-of-turn must be reduced gradually to ensure
for this. For this maneuver, pick a square or rectangular field, that upon completion of the turn, the crosswind ground track
or an area bounded on four sides by section lines or roads, continues to be the same distance from the edge of the field.
with sides approximately a mile in length. The area selected Upon completion of the turn, the helicopter should be level
should be well away from other air traffic. Fly the maneuver and crabbed into the wind in order to maintain the proper
approximately 500 to 800 feet above the ground, which is ground track. Keep in mind that in order to maintain proper
the altitude usually required for an airport traffic pattern. If ground track the helicopter may have to be flown almost
the student finds it difficult to maintain a proper ground track sideways depending on the amount of wind. The forward
at that higher altitude, lower the altitude for better ground cyclic that is applied for airspeed will be in the direction of
reference until they feel more comfortable and are able to the intended flight path. For this example, it will be in the
grasp the concept better. Altitude can be varied up to 800 direction of the downwind corner of the field. However, since
feet as proficiency improves. the wind is now pushing the helicopter away from the field,
establish the proper drift correction by heading slightly into
Fly the helicopter parallel to and at a uniform distance, about the wind. Therefore, the turn should be greater than a 90°
one-fourth to one-half mile, from the field boundaries, and change in heading (position 3). If the turn has been made
not directly above the boundaries. For best results, position properly, the field boundary again appears to be one-fourth
flightpath outside the field boundaries just far enough away to one-half mile away. While on the crosswind leg, the wind
that they may be easily observed from either pilot seat by correction should be adjusted, as necessary, to maintain a
looking out the side of the helicopter. If an attempt is made uniform distance from the field boundary (position 4).
to fly directly above the edges of the field, there will be no
9-14
Enter 45° to downwind
Start turn at boundary No crab Complete turn at boundary
2 1 11 Turn more than 90°
Track with no wind correction Turn more than 90°—roll Track with no wind correction 10
3 out with crab established Start turn
Complete turn at boundary at boundary
Crab into wind Wind Crab into wind
4
Start turn Turn less than 90°—roll out with crab established 9
at boundary Complete turn at boundary
5 Turn less than 90°
6 7 8
No crab Start turn at boundary
Complete turn at boundary
Figure 9-15. Example of a rectangular course. 3. Uncoordinated flight control application.
As the next field boundary is being approached (position 5), 4. Improper correction for wind drift.
plan for the next turn. Since a wind correction angle is being
held into the wind and toward the field, this next turn requires 5. Failure to maintain selected altitude and airspeed.
a turn of less than 90°. Since there is now a headwind, the
groundspeed decreases during the turn, the bank initially must 6. Selection of a ground reference with no suitable
be medium and progressively decrease as the turn proceeds. emergency landing area within gliding distance.
To complete the turn, time the rollout so that the helicopter
becomes level at a point aligned with the corner of the field 7. Not flying a course parallel to the intended area (e.g.,
just as the longitudinal axis of the helicopter again becomes traffic pattern or square field).
parallel to the field boundary (position 6). The distance from
the field boundary should be the same as on the other sides S-Turns
of the field. Another training maneuver to use is the S-turn, which helps
correct for wind drift in turns. This maneuver requires turns
Continue to evaluate each turn and determine the steepness to the left and right.
or shallowness based on the winds. It is also important to
remember that as the bank angles are adjusted in the turn, Technique
the pilot is subsequently forced to make changes with the The pilot can choose to use a road, a fence, or a railroad
flight controls. for a reference line. Regardless of what is used, it should
be straight for a considerable distance and should extend
Common Errors as nearly perpendicular to the wind as possible. The object
of S-turns is to fly a pattern of two half circ les of equal size
1. Faulty entry technique. on opposite sides of the reference line. [Figure 9-16] The
2. Poor planning, orientation, and/or division of attention.
9-15
Wind is to an upwind heading, the shallower the bank. In addition
to varying the angle of bank to correct for drift in order to
Points of shallowest bank 3 4 maintain the proper radius of turn, the helicopter must also
1 Points of steepest bank 5 be flown with a drift correction angle (crab) in relation to its
ground track; except, of course, when it is on direct upwind
Point of steepest bank 2 or downwind headings or there is no wind.
Figure 9-16. S-turns across a road. One would normally think of the fore and aft axis of the
helicopter as being tangent to the ground track pattern at
maneuver should be performed at a constant altitude between each point. However, this is not the case. During the turn on
500 and 800 feet above the terrain. As mentioned previously, the upwind side of the reference line (side from which the
if the student pilot is having a difficult time maintaining the wind is blowing), crab the nose of the helicopter toward the
proper altitude and airspeed, have him or her attempt the outside of the circle. During the turn on the downwind side
S-turn at a lower altitude, providing better ground reference. of the reference line (side of the reference line opposite to the
The discussion that follows is based on choosing a reference direction from which the wind is blowing), crab the nose of
line perpendicular to the wind and starting the maneuver with the helicopter toward the inside of the circle. In either case, it
the helicopter facing downwind. is obvious that the helicopter is being crabbed into the wind
just as it is when trying to maintain a straight ground track.
The amount of crab depends on the wind velocity and how
close the helicopter is to a crosswind position. The stronger
the wind is, the greater the crab angle is at any given position
for a turn of a given radius. The more nearly the helicopter
is to a crosswind position, the greater the crab angle. The
maximum crab angle should be at the point of each half circle
farthest from the reference line.
As the helicopter crosses the reference line, immedi A standard radius for S-turns cannot be specified, since the
ately establish a bank. This initial bank is the steepest radius depends on the airspeed of the helicopter, the velocity
used throughout the maneuver since the helicopter is of the wind, and the initial bank chosen for entry. The only
headed directly downwind and the groundspeed is greatest standard is crossing the ground reference line straight and
(position 1). Gradually reduce the bank, as necessary, to level, and having equal radius semi-circles on both sides.
describe a ground track of a half circle. Time the turn so
that, as the rollout is completed, the helicopter is crossing Common Errors
the reference line perpendicular to it and heading directly
upwind (position 2). Immediately enter a bank in the opposite 1. Using antitorque pedal pressures to assist turns.
direction to begin the second half of the “S” (position 3).
Since the helicopter is now on an upwind heading, this bank 2. Slipping or skidding in the turn.
(and the one just completed before crossing the reference
line) is the shallowest in the maneuver. Gradually increase 3. An unsymmetrical ground track during S-turns across
the bank, as necessary, to describe a ground track that is a a road.
half circle identical in size to the one previously completed on
the other side of the refere nce line (position 4). The steepest 4. Improper correction for wind drift.
bank in this turn should be attained just prior to rollout when
the helicopter is approaching the reference line nearest the 5. Failure to maintain selected altitude or airspeed.
downwind heading. Time the turn so that as the rollout is
complete, the helicopter is perpendicular to the reference 6. Excessive bank angles.
line and is again heading directly downwind (position 5).
Turns Around a Point
In summary, the angle of bank required at any given This training maneuver requires flying constant radius
point in the maneuver is dependent on the grounds peed. turns around a preselected point on the ground using a bank
The faster the groundspeed is, the steeper the bank is; the angle of approximately 30°–45°, while maintaining both
slower the groundspeed is, the shallower the bank is. To a constant altitude and the same distance from the point
express it another way, the more nearly the helicopter is to a throughout the maneuver. [Figure 9-17] The objective, as in
downwind heading, the steeper the bank; the more nearly it other ground reference maneuvers, is to develop the ability
to subconsciously control the helicopter while dividing
attention between flightpath, how the winds are affecting
the turn and ground references, and watching for other air
9-16
Steeper bankWind Just as S-turns require that the helicopter be turned into the
Upwind half of circle Steepest bank wind in addition to varying the bank, so do turns around a
point. During the downwind half of the circle, the helicopter’s
Shallowest bank nose must be progressively turned toward the inside of the
circle; during the upwind half, the nose must be progressively
turned toward the outside. The downwind half of the turn
around the point may be compared to the downwind side of
the S-turn, while the upwind half of the turn around a point
may be compared to the upwind side of the S-turn.
Downwind half of circle Upon gaining experience in performing turns around a point
and developing a good understanding of the effects of wind
Shallower bank drift and varying of the bank angle and wind correction angle
as required, entry into the maneuver may be from any point.
Figure 9-17. Turns around a point. When entering this maneuver at any point, the radius of the
turn must be carefully selected, taking into account the wind
traffic in the vicinity. This is also used in high reconnaissance, velocity and groundspeed so that an excessive bank is not
observation, and photography flight. required later to maintain the proper ground track.
Technique S-Turn Common Errors
The factors and principles of drift correction that are involved
in S-turns are also applicable to this maneuver. As in other 1. Faulty entry technique.
ground track maneuvers, a constant radius around a point
requires the pilot to change the angle of bank constantly 2. Poor planning, orientation, or division of attention.
and make numerous control changes to compensate for
the wind. The closer the helicopter is to a direct downwind 3. Uncoordinated flight control application.
heading at which the groundspeed is greatest, the steeper the
bank and the greater the rate of turn required to establish the 4. Improper correction for wind drift.
proper wind correction angle. The closer the helicopter is to
a direct upwind heading at which the groundspeed is least, 5. Failure to maintain selected altitude or airspeed.
the shallower the bank and the lower the rate of turn required
to establish the proper wind correction angle. Therefore, 6. Failure to maintain an equal distance around the point.
throughout the maneuver, the bank and rate of turn must
be varied gradually and in proportion to the groundspeed 7. Excessive bank angles.
corrections made for the wind.
Traffic Patterns
The point selected for turns should be prominent and easily
distinguishable, yet small enough to present a precise A traffic pattern promotes safety by establishing a common
reference. Isolated trees, crossroads, or other similar small track to help pilots determine their landing order and provide
landmarks are usually suitable. The point should be in an area common reference. A traffic pattern is also useful to control
away from communities, livestock, or groups of people on the flow of traffic, particularly at airports without operating
the ground to prevent possible annoyance or hazard to others. control towers. It affords a measure of safety, separation,
Since the maneuver is performed between 500 and 800 feet protection, and administrative control over arriving,
AGL, the area selected should also afford an opportunity departing, and circling aircraft. Due to specialized operating
for a safe emergency autorotation in the event it becomes characteristics, airplanes and helicopters do not mix well
necessary. in the same traffic environment. At multiple-use airports,
regulation states that helicopters should always avoid the
flow of fixed-wing traffic. To do this, be familiar with the
patterns typically flown by airplanes. In addition, learn how
to fly these patterns in case air traffic control (ATC) requests
a fixed-wing traffic pattern be flown.
A normal airplane traffic pattern is rectangular, has five named
legs, and a designated altitude, usually 1,000 feet AGL. While
flying the traffic pattern, pilots should always keep in mind
noise abatement rules and flying friendly to avoid dwellings
9-17
and livestock. A pattern in which all turns are to the left is Traffic pattern entry procedures at an airport with an operating
called a standard pattern. [Figure 9-18] The takeoff leg (item control tower are specified by the controller. At uncontrolled
1) normally consists of the aircraft’s flightpath after takeoff. airports, traffic pattern altitudes and entry procedures may
This leg is also called the upwind leg. Turn to the crosswind vary according to established local procedures. Helicopter
leg (item 2) after passing the departure end of the runway when pilots should be aware of the standard airplane traffic
at a safe altitude. Fly the downwind leg (item 3) parallel to the pattern and avoid it. Generally, helicopters make a lower
runway at the designated traffic pattern altitude and distance altitude pattern opposite from the fixed wing pattern and
from the runway. Begin the base leg (item 4) at a point selected make their approaches to some point other than the runway
according to other traffic and wind conditions. If the wind is in use by the fixed wing traffic. Chapter 7 of the Airplane
very strong, begin the turn sooner than normal. If the wind flying Handbook, FAA-H-8083-3 discusses this in greater
is light, delay the turn to base. The final approach (item 5) detail. For information concerning traffic pattern and landing
is the path the airc raft flies immediately prior to touchdown. direction, utilize airport advisory service or UNICOM, when
available.
Base leg 4 3 Downwind leg The standard departure procedure when using the fixed-
2 Crosswind leg wing traffic pattern is usually a straight-out, downwind, or
right-hand departure. When a control tower is in operation,
09 request the type of departure desired. In most cases, helicopter
departures are made into the wind unless obstacles or traffic
5 Final approach leg 1 Takeoff leg (upwind) dictate otherwise. At airports without an operating control
tower, comply with the departure procedures established for
that airport, if any.
Figure 9-18. A standard fixed-wing traffic pattern consists of left An accepted helicopter traffic pattern is flown at 500 feet
turns, has five designated legs, and is flown at 1,000' AGL. AGL and consists of right turns. [Figure 9-19] This keeps the
helicopter out of the flow of fixed-wing traffic. A helicopter
Flying a fixed wing traffic pattern at 1,000 feet AGL upon may take off from a helipad into the wind with a turn to the
the request of ATC should not be a problem for a helicopter right after 300 feet AGL or as needed to be in range of forced
unless conducting specific maneuvers that require specific landing areas. When 500 feet AGL is attained, a right turn
altitudes. There are variations at different localities and at to parallel the takeoff path is made for the downwind. Then,
airports with operating control towers. For example, air traffic as the intended landing point is about 45 degrees behind the
control (ATC) may have airplanes in a left turn pattern as abeam position of the helicopter, a right turn is made and a
airplane pilots are usually seated in the left seat and a right descent is begun from downwind altitude to approximately
turn pattern for helicopters as those pilots are usually in the 300 feet AGL for a base leg.
right seat. This arrangement affords the best view from each
of the cockpits. Always consult the Airport/Facility Directory 3 Downwind leg
for the traffic pattern procedures at your airport/heliport. 4 Base leg
When approaching an airport with an operating control tower Crosswind leg 2
in a helicopter, it is possible to expedite traffic by stating
intentions. The communication consists of: 27
1. The helicopter’s call sign, “Helicopter 8340J.” 1 Takeoff leg (upwind) 5 Final approach leg
2. The helicopter’s position, “10 miles west.” Figure 9-19. A standard helicopter traffic pattern consists of right
turns, has 5 designated legs, and is flown at 500' AGL.
3. The “request for landing and hover to ...”
As the helicopter nears the final approach path, the turn to
To avoid the flow of fixed-wing traffic, the tower often final should be made considering winds and obstructions.
clears direct to an approach point or to a particular runway
intersection nearest the destination point. At uncontrolled
airports, if at all possible, adhere to standard practices and
patterns.
9-18
Depending on obstructions and forced landing areas, the final Reference point
approach may need to be accomplished from as high as 500 Imaginary centerline
feet AGL. The landing area should always be in sight and
the angle of approach should never be too high (indicating
that the base leg is too close) to the landing area or too low
(indicating that the landing area is too far away).
Approaches
An approach is the transition from traffic pattern altitude
to either a hover or to the surface. The approach should
terminate at the hover altitude with the rate of descent and
groundspeed reaching zero at the same time. Approaches
are categorized according to the angle of descent as normal,
steep, or shallow. In this chapter, concentration is on the
normal approach. Steep and shallow approaches are discussed
in the next chapter.
Use the type of approach best suited to the existing conditions.
These conditions may include obstacles, size and surface of
the landing area, density altitude, wind direction and speed,
and weight. Regardless of the type of approach, it should
always be made to a specific, predetermined landing spot.
Normal Approach to a Hover Figure 9-20. Plan the turn to final so the helicopter rolls out on an
A normal approach uses a descent profile of between 7° and imaginary extension of the centerline for the final approach path.
12° starting at approximately 300–500 feet AGL. This path should neither angle to the landing area, as shown by
the helicopter on the left, nor require an S-turn, as shown by the
Technique helicopter on the right.
On final approach, at the recommended approach airspeed the collective to maintain approach angle. Use the cyclic to
and at approximately 300 feet AGL, the helicopter should maintain a rate of closure equivalent to a brisk walk.
be on the correct ground track (or ground alignment) for
the intended landing site, but the axis of the helicopter does At approximately 25 knots, depending on wind, the helicopter
not have to be aligned until about 100' AGL to facilitate a begins to lose effective translational lift. To compensate for
controlled approach. [Figure 9-20] Just prior to reaching loss of effective translational lift, increase the collective to
the desired approach angle, begin the approach by lowering maintain the approach angle, while maintaining the proper
the collective sufficiently to get the helicopter decelerating rpm. The increase of collective pitch tends to make the nose
and descending down the approach angle. With the decrease rise, requiring forward cyclic to maintain the proper rate of
in the collective, the nose tends to pitch down, requiring closure.
aft cyclic to maintain the recommended approach airspeed
attitude. Adjust antitorque pedals, as necessary, to maintain As the helicopter approaches the recommended hover
trim. Pilots should visualize the angle from the landing altitude, increase the collective sufficiently to maintain the
point to the middle of the skids or landing gear underneath hover. Helicopters require near maximum power to land
them in the cockpit and maneuver the helicopter down that because the inertia of the helicopter in a descent must be
imaginary slope until the helicopter is at a hover centered overcome by lift in the rotor system. At the same time, apply
over the landing point, or touching down centered on the aft cyclic to stop any forward movement while controlling
landing point. The most important standard for a normal the heading with antitorque pedals.
approach is maintaining a consistent angle of approach to
the termination point. The collective controls the angle of
approach. Use the cyclic to control the rate of closure or how
fast the helicopter is moving towards the touchdown point.
Maintain entry airspeed until the apparent groundspeed and
rate of closure appear to be increasing. At this point, slowly
begin decelerating with slight aft cyclic, and smoothly lower
9-19
Common Errors Crosswind During Approaches
During a crosswind approach, crab into the wind. At
1. Failing to maintain proper rpm during the entire approximately 50 feet of altitude, use a slip to align the
approach. fuselage with the ground track. The rotor is tilted into the
wind with cyclic pressure so that the sideward movement
2. Improper use of the collective in controlling the angle of the helicopter and wind drift counteracts each other.
of descent. Maintain the heading and ground track with the antitorque
pedals. Under crosswind approaches, ground track is always
3. Failing to make antitorque pedal corrections to controlled by the cyclic movement. The heading of the
compensate for collective changes during the helicopter in hovering maneuvers is always controlled by
approach. the pedals. The collective controls power, which is altitude
at a hover. This technique should be used on any type of
4. Maintaining a constant airspeed on final approach crosswind approach, whether it is a shallow, normal, or
instead of an apparent brisk walk. steep approach.
5. Failing to simultaneously arrive at hovering altitude Go-Around
and attitude with zero groundspeed.
A go-around is a procedure for remaining airborne after
6. Low rpm in transition to the hover at the end of the an intended landing is discontinued. A go-around may be
approach. necessary when:
7. Using too much aft cyclic close to the surface, which • Instructed by the control tower.
may result in tail rotor strikes.
• Traffic conflict occurs.
8. Failure to crab above 100’AGL and slip below
100’AGL. • The helicopter is in a position from which it is not
safe to continue the approach. Any time an approach
Normal Approach to the Surface is uncomfortable, incorrect, or potentially dangerous,
A normal approach to the surface or a no-hover landing is abandon the approach. The decision to make a go-
often used if loose snow or dusty surface conditions exist. around should be positive and initiated before a critical
These situations could cause severely restricted visibility, or situation develops. When the decision is made, carry it
the engine could possibly ingest debris when the helic opter out without hesitation. In most cases, when initiating
comes to a hover. The approach is the same as the normal the go-around, power is at a low setting. Therefore,
approach to a hover; however, instead of termin ating at a the first response is to increase collective to takeoff
hover, continue the approach to touchdown. Touchdown power. This movement is coordinated with the throttle
should occur with the skids level, zero groundspeed, and a to maintain rpm, and with the proper antitorque pedal
rate of descent approaching zero. to control heading. Then, establish a climb attitude
and maintain climb speed to go around for another
Technique approach.
As the helicopter nears the surface, increase the collective, as
necessary, to cushion the landing on the surface, terminate in Chapter Summary
a skids-level attitude with no forward movement.
This chapter introduced basic flight maneuvers and the
Common Errors techniques to perform each of them. Common errors and why
they happen were also described to help the pilot achieve a
1. Terminating to a hover, and then making a vertical better understanding of the maneuver.
landing.
2. Touching down with forward movement.
3. Approaching too slow, requiring the use of excess ive
power during the termination.
4. Approaching too fast, causing a hard landing
5. Not maintaining skids aligned with direction of travel
at touchdown. Any movement or misalignment of the
skids or gear can induce dynamic rollover
9-20
Chapter 10
Advanced
Flight Maneuvers
Introduction
The maneuvers presented in this chapter require more skill
and understanding of the helicopter and the surrounding
environment. When performing these maneuvers, a pilot
is probably taking the helicopter to the edge of the safe
operating envelope. Therefore, if you are ever in doubt about
the outcome of the maneuver, abort the mission entirely or
wait for more favorable conditions.
10-1
Reconnaissance Procedures during this evaluation. Besides determining the best departure
path and indentifying all hazards in the area, select a route
When planning to land or take off at an unfam iliar site, that gets the helicopter from its present position to the takeo ff
gather as much information as possible about the area. point while avoiding all hazards, especially to the tail rotor
Reconnaissance techniques are ways of gathering this and landing gear.
information.
Some things to consider while formulating a takeoff plan
High Reconnaissance are the aircraft load, height of obstacles, the shape of the
The purpose of conducting a high reconnaissance is to area, direction of the wind, and surface conditions. Surface
determine direction and speed of the wind, a touchdown conditions can consist of dust, sand and snow, as well as
point, suitability of the landing area, approach and departure mud and rocks. Dust landings and snow landings can lead
axes, and obstacles for both the approach and departure. to a brownout or whiteout condition, which is the loss of
The pilot should also give particular consideration to forced the horizon reference. Disorientation may occur, leading
landing areas in case of an emergency. to ground contact, often with fatal results. Taking off or
landing on uneven terrain, mud, or rocks can cause the tail
Altitude, airspeed, and flight pattern for a high reconn aissance rotor to strike the surface or if the skids get caught can lead
are governed by wind and terrain features. It is important to to dynamic rollover. If the helicopter is heavily loaded,
strike a balance between a reconnaissance conducted too high determine if there is sufficient power to clear the obstacles.
and one too low. It should not be flown so low that a pilot Sometimes it is better to pick a path over shorter obstacles
must divide attention between studying the area and avoiding than to take off directly into the wind. Also evaluate the shape
obstructions to flight. A high reconnaissance should be flown of the area so that a path can be chosen that will provide you
at an altitude of 300 to 500 feet above the surface. A general the most room to maneuver and abort the takeoff if necessary.
rule to follow is to ensure that sufficient altitude is available Positioning the helicopter to the most downwind portion of
at all times to land into the wind in case of engine failu re. In the confined area gives the pilot the most distance to clear
addition, a 45° angle of observation generally allows the best obstacles. Wind analysis also helps determine the route of
estimate of the height of barriers, the presence of obstacles, takeoff. The prevailing wind can be altered by obstructions
the size of the area, and the slope of the terrain. Always on the departure path and can significantly affect aircraft
maintain safe altitudes and airspeeds, and keep a forced performance. There are several ways to check the wind
landing area within reach whenever possible. direction before taking off. One technique is to watch the tops
of the trees; another is to look for any smoke in the area. If
Low Reconnaissance there is a body of water in the area, look to see which way the
A low reconnaissance is accomplished during the approach to water is rippling. If wind direction is still in question revert
the landing area. When flying the approach, verify what was back to the last report that was received by either ATIS or
observed in the high reconnaissance, and check for anything airport tower.
new that may have been missed at a higher altitude, such as
wires and their supporting structures (poles, towers, etc.), Maximum Performance Takeoff
slopes, and small crevices. If the pilot determines that the
area chosen is safe to land in, the approach can be continued. A maximum performance takeoff is used to climb at a steep
However, the decision to land or go around must be made angle to clear barriers in the flightpath. It can be used when
prior to decelerating below effective translational lift (ETL), taking off from small areas surrounded by high obstacles.
or before descending below the barriers surrounding the Allow for a vertical takeoff, although not preferred, if
confined area. obstruction clearance could be in doubt. Before attempting
a maximum performance takeoff, know thoroughly the
If a decision is made to complete the approach, termin ate capabilities and limitations of the equipment. Also consider
the landing to a hover in order to check the landing point the wind velocity, temperature, density altitude, gross weight,
carefully before lowering the helicopter to the surface. center of gravity (CG) location, and other factors affecting
Under certain conditions, it may be desirable to continue the pilot technique and the performance of the helicopter.
approach to the surface. Once the helicopter is on the ground,
maintain operating rpm until the stability of the helicopter To accomplish this type of takeoff safely, there must be
has been checked to be sure it is in a secure and safe position. enough power to hover OGE in order to prevent the helicopter
from sinking back to the surface after becoming airborne.
Ground Reconnaissance A hover power check can be used to determine if there is
Prior to departing an unfamiliar location, make a detailed sufficient power available to accomplish this maneuver.
analysis of the area. There are several factors to consider
10-2
The angle of climb for a maximum performance take in pedal pressure to maintain heading (position 2). Use the
off depends on existing conditions. The more critical the cyclic, as necessary, to control movement toward the desired
conditions are, such as high density altitudes, calm winds, flightpath and, therefore, climb angle during the maneuver
and high gross weights, the shallower the angle of climb is. In (position 3). Maintain rotor rpm at its maxim um, and do
light or no wind conditions, it might be necessary to operate not allow it to decrease since you would probably need to
in the crosshatched or shaded areas of the height/velocity lower the collective to regain it. Maintain these inputs until
diagram during the beginning of this maneuver. Therefore, the helicopter clears the obstacle, or until reaching 50 feet
be aware of the calculated risk when operating in these areas. for demonstration purposes (position 4). Then, establish a
An engine failure at a low altitude and airspeed could place normal climb attitude and power setting (position 5). As
the helicopter in a dangerous position, requiring a high degree in any maximum performance maneuver, the techniques
of skill in making a safe autorotative landing. used affect the actual results. Smooth, coordinated inputs
coupled with precise control allow the helicopter to attain
Technique its maximum performance.
Before attempting a maximum performance takeoff,
reposition the helicopter to the most downwind area to allow a An acceptable but less preferred variation is to perform a
longer takeoff climb, then bring the helicopter to a hover, and vertical takeoff. This technique allows the pilot to descend
determine the excess power available by noting the difference vertically back into the confined area if the helicopter
between the power available and that required to hover. does not have the performance to clear the surrounding
Also, perform a balance and flight control check and note obstacles. During this maneuver, the helicopter must climb
the position of the cyclic. If the takeoff path allows, position vertically and not be allowed to accelerate forward until the
the helicopter into the wind and return the helicopter to the surrounding obstacles have been cleared. If not, a situation
surface. Normally, this maneuver is initiated from the surface. may develop where the helicopter does not have sufficient
After checking the area for obstacles and other aircraft, select climb performance to avoid obstructions and may not have
reference points along the takeoff path to maintain ground power to descend back to the takeoff point. The vertical
track. Also consider alternate routes in case the maneuver is takeoff might not be as efficient as the climbing profile, but
not possible. [Figure 10-1] is much easier to abort from a vertical position directly over
the landing point. The vertical takeoff however places the
5 helicopter in the avoid are of the height/velocity diagram for
a longer time. This maneuver requires hover OGE power to
accomplish.
4 Common Errors
3 1. Failure to consider performance data, including height/
velocity diagram.
2
2. Nose too low initially causing horizontal flight rather
1 than more vertical flight.
Figure 10-1. Maximum performance takeoff. 3. Failure to maintain maximum permissible rpm.
Begin the takeoff by getting the helicopter light on the 4. Abrupt control movements.
skids (position 1). Pause and neutralize all aircraft move
ment. Slowly increase the collective and position the 5. Failure to resume normal climb power and airspeed
cyclic to lift off in a 40 knot attitude. This is approximately after clearing the obstacle.
the same attitude as when the helicopter is light on the
skids. Continue to increase the collective slowly until the Running/Rolling Takeoff
maximum power available is reached (takeoff power is
normally 10 percent above power required for hover). This A running takeoff in helicopter with fixed landing gear,
large collective movement requires a substantial increase such as skids, skis or floats, or a rolling takeoff in a
wheeled helicopter is sometimes used when conditions of
load and/or density altitude prevent a sustained hover at
normal hovering altitude. For wheeled helicopters, a rolling
takeoff is sometimes used to minimize the downwash
created during a takeoff from a hover. Avoid a running/
rolling maneuver if there is not sufficient power to hover,
at least momentarily. If the helicopter cannot be hovered,
10-3
its performance is unpredictable. If the helicopter cannot The height/velocity parameters should be respected at all
be raised off the surface at all, sufficient power might not times. The helicopter should be flown to a suitable altitude
be available to accomplish the maneuver safely. If a pilot to allow a safe acceleration in accordance with the height/
cannot momentarily hover the helicopter, wait for conditions velocity diagram.
to improve or off-load some of the weight.
Common Errors
To accomplish a safe running or rolling takeoff, the surface
area must be of sufficient length and smoothness, and there 1. Failing to align heading and ground track to keep
cannot be any barriers in the flightpath to interfere with a surface friction to a minimum.
shallow climb.
2. Attempting to become airborne before obtaining
Technique effective translational lift.
Refer to Figure 10-2. To begin the maneuver, first align the
helicopter to the takeoff path. Next, increase the throttle to 3. Using too much forward cyclic during the surface run.
obtain takeoff rpm, and increase the collective smoothly
until the helicopter becomes light on the skids or landing 4. Lowering the nose too much after becoming airb orne,
gear (position 1). If taking off from the water, ensure that resulting in the helicopter settling back to the surface.
the floats are mostly out of the water. Then, move the cyclic
slightly forward of the neutral hovering position, and apply 5. Failing to remain below the recommended altitude
additional collective to start the forward movement (position until airspeed approaches normal climb speed.
2). To simulate a reduced power condition during practice,
use one to two inches less manifold pressure, or three to five Rapid Deceleration or Quick Stop
percent less torque than that required to hover. The landing
This maneuver is used to decelerate from forward flight to a
hover. It is often used to abort takeoffs, to stop if something
blocks the helicopter flightpath, or simply to terminate an air
taxi maneuver, as mentioned in the Aeronautical Information
Manual (AIM). A quick stop is usually practiced on a runway,
taxiway, or over a large grassy area away from other traffic
or obstacles.
4 Technique
1 23 The maneuver requires a high degree of coordination of
all controls. It is practiced at an altitude that permits a safe
Figure 10-2. Running/rolling takeoff. clearance between the tail rotor and the surface throughout
the maneuver, especially at the point where the pitch attitude
gear must stay aligned with the takeoff direction until the is highest. The altitude at completion should be no higher
helicopter leaves the surface to avoid dynamic rollover. than the maximum safe hovering altitude prescribed by that
Maintain a straight ground track with lateral cyclic and particular helicopter’s manufacturer. In selecting an altitude
heading with antitorque pedals until a climb is established. at which to begin the maneuver, take into account the overall
As effective translational lift is gained, the helicopter length of the helicopter and its height-velocity diagram. Even
becomes airborne in a fairly level attitude with little or no though the maneuver is called a rapid deceleration or quick
pitching (position 3). Maintain an altitude to take advantage stop, it is performed slowly and smoothly with the primary
of ground effect, and allow the airspeed to increase toward emphasis on coordination.
normal climb speed. Then, follow a climb profile that takes
the helicopter through the clear area of the height/velocity During training, always perform this maneuver into the wind
diagram (position 4). During practice maneuvers, after having [Figure 10-3, position 1]. After leveling off at an altitude
climbed to an altitude of 50 feet, establish the normal climb between 25 and 40 feet, depending upon the manufacturer’s
power setting and attitude. recommendations, accelerate to the desired entry speed,
which is approximately 45 knots for most training helicopters
NOTE: It should be remembered that if a running takeoff is (position 2). The altitude chosen should be high enough to
necessary for most modern helicopters, the helicopter is very avoid danger to the tail rotor during the flare, but low enough
close to, or has exceeded the maximum operating weight for to stay out of the hazardous areas of that helicopter’s height-
the conditions (i.e., temperature and altitude). velocity diagram throughout the maneuver. In addition, this
altitude should be low enough that the helicopter can be
brought to a hover during the recovery.
10-4
1 2 34
5
Figure 10-3. Rapid deceleration or quick stop. during the recovery, resulting in excessive manifold
pressure or an overtorque situation when collective
At position 3, initiate the deceleration by applying aft cyclic pitch is applied rapidly.
to reduce forward groundspeed. Simultaneously, lower the
collective, as necessary, to counteract any climbing tendency. 7. Failing to maintain a safe clearance over the terrain.
The timing must be exact. If too little collective is taken out
for the amount of aft cyclic applied, the helicopter climbs. 8. Using antitorque pedals improperly, resulting in erratic
If too much downward collective is applied, the helicopter heading changes.
will descend. A rapid application of aft cyclic requires an
equally rapid application of down collective. As collective 9. Using an excessively nose-high attitude.
pitch is lowered, apply proper antitorque pedal pressure to
maintain heading, and adjust the throttle to maintain rpm. Steep Approach
The G loading on the rotor system depends on the pitch-up
attitude. If the attitude is too high, the rotor system may stall A steep approach is used primarily when there are obstacles
and cause the helicopter to impact the surface. in the approach path that are too high to allow a normal
approach. A steep approach permits entry into most confined
After attaining the desired speed (position 4), initiate the areas and is sometimes used to avoid areas of turbulence
recovery by lowering the nose and allowing the helicopter around a pinnacle. An approach angle of approximately 13°
to descend to a normal hovering altitude in level flight and to 15° is considered a steep approach. [Figure 10-4] Caution
zero groundspeed (position 5). During the recovery, increase must be exercised to avoid the parameters for settling with
collective pitch, as necessary, to stop the helicopter at normal power (20–100 percent of available power applied, airspeed
hovering altitude, adjust the throttle to maintain rpm, and apply of less than 10 knots, and a rate of descent greater than 300
proper antitorque pedal pressure, as necessary, to maintain fpm). For additional information on settling with power,
heading. During the maneuver, visualize rotating around the refer to Chapter 11, Helicopter Emergencies and Hazards.
tail rotor until a normal hovering altitude is reached.
Common Errors 1 15° Approach angle
2 3
1. Initiating the maneuver by lowering the collective
without aft cyclic pressure to maintain altitude. 4
2. Initially applying aft cyclic stick too rapidly, causing Figure 10-4. Steep approach to a hover.
the helicopter to balloon (climb).
3. Failing to effectively control the rate of deceleration
to accomplish the desired results.
4. Allowing the helicopter to stop forward motion in a
tail-low attitude.
5. Failing to maintain proper rotor rpm.
6. Waiting too long to apply collective pitch (power)
10-5
Technique Common Errors
On final approach, maintain track with the intended
touchdown point and into the wind as much as possible at 1. Failing to maintain proper rpm during the entire
the recommended approach airspeed (position 1). When approach.
intercepting an approach angle of 13° to 15°, begin the
approach by lowering the collective sufficiently to start 2. Using collective improperly in maintaining the
the helicopter descending down the approach path and selected angle of descent.
decelerating (position 2). Use the proper antitorque pedal for
trim. Since this angle is steeper than a normal approach angle, 3. Failing to make antitorque pedal corrections to
reduce the collective more than that required for a normal compensate for collective pitch changes during the
approach. Continue to decelerate with slight aft cyclic and approach.
smoothly lower the collective to maintain the approach angle.
4. Slowing airspeed excessively in order to remain on
The intended touchdown point may not always be visible the proper angle of descent.
throughout the approach, especially when landing to a hover.
Pilots must learn to cue in to other references that are parallel 5. Failing to determine when effective translational lift
to the intended landing area that will help them maintain is being lost.
ground track and position.
6. Failing to arrive at hovering altitude and attitude, and
Constant management of approach angle and airspeed is zero groundspeed almost simultaneously.
essential to any approach. Aft cyclic is required to decelerate
sooner than a normal approach, and the rate of closure 7. Utilizing low rpm in transition to the hover at the end
becomes apparent at a higher altitude. Maintain the approach of the approach.
angle and rate of descent with the collective, rate of closure
with the cyclic, and trim with antitorque pedals. 8. Using too much aft cyclic close to the surface, which
may result in the tail rotor striking the surface.
The helicopter should be kept in trim just prior to loss of
effective translational lift (approximately 25 knots). Below 9. Failure to align landing gear with direction of travel
100' AGL, the antitorque pedals should be adjusted to align no later than beginning of loss of translational lift.
the helicopter with the intended touchdown point. Visualize
the location of the tail rotor behind the helicopter and fly the Shallow Approach and Running/Roll-On
landing gear to 3 feet above the intended landing point. In Landing
small confined areas, the pilot must precisely position the
helicopter over the intended landing area. Therefore, the Use a shallow approach and running landing when a
approach must stop at that point. high density altitude, a high gross weight condition, or
some combination thereof, is such that a normal or steep
Loss of effective translational lift occurs higher in a steep approach cannot be made because of insufficient power
approach (position 3), requiring an increase in the collective to hover. [Figure 10-5] To compensate for this lack of
to prevent settling, and more forward cyclic to achieve power, a shallow approach and running landing makes use
the proper rate of closure. Once the intended landing area of translational lift until surface contact is made. If flying a
is reached, terminate the approach to a hover with zero wheeled helicopter, a roll-on landing can be used to minimize
groundspeed (position 4). If the approach has been executed the effect of downwash. The glide angle for a shallow
properly, the helicopter will come to a halt at a hover altitude approach is approximately 3° to 5°. This angle is similar to
of 3 feet over the intended landing point with very little the angle used on an ILS approach. Since the helicopter is
additional power required to hold the hover. sliding or rolling to a stop during this maneuver, the landing
area should be smooth and the landing gear must be aligned
with the direction of travel to prevent dynamic rollover and
must be long enough to accomplish this task. After landing,
ensure that the pitch of the rotor blades is not to far aft as the
main rotor blades could contact the tailboom.
The pilot must aware that any wind effect is lost once the 5° Approach angle
aircraft has descended below the barriers surrounding a 1 2 3 4
confined area, causing the aircraft to settle more quickly.
Additional power may be needed on a strong wind condition
as the helicopter descends below the barriers.
Figure 10-5. Shallow approach and running landing.
10-6
Technique Common Errors
A shallow approach is initiated in the same manner as the
normal approach except that a shallower angle of descent is 1. Assuming excessive nose-high attitude to slow the
maintained. The power reduction to initiate the desired angle helicopter near the surface.
of descent is less than that for a normal approach since the
angle of descent is less (position 1). 2. Utilizing insufficient collective and throttle to cushion
a landing.
As the collective is lowered, maintain heading with proper
antitorque pedal pressure and rpm with the throttle. Maintain 3. Failure to maintain heading resulting in a turning or
approach airspeed until the apparent rate of closure appears pivoting motion.
to be increasing. Then, begin to slow the helicopter with aft
cyclic (position 2). 4. Failure to add proper antitorque pedal as collective is
added to cushion landing, resulting in a touchdown
As in normal and steep approaches, the primary control while the helicopter is moving sideward.
for the angle and rate of descent is the collective, while the
cyclic primarily controls the groundspeed. However, there 5. Failure to maintain a speed that takes advantage of
must be a coordination of all the controls for the maneuver effective translational lift.
to be accomplished successfully. The helicopter should
arrive at the point of touchdown at or slightly above effective 6. Touching down at an excessive groundspeed for the
translational lift. Since translational lift diminishes rapidly existing conditions. (Some helicopters have maximum
at slow airspeeds, the deceleration must be coordinated touchdown groundspeeds.)
smoothly, at the same time keeping enough lift to prevent
the helicopter from settling abruptly. 7. Failure to touch down in the appropriate attitude
necessary for a safe landing. Appropriate attitude is
Just prior to touchdown, place the helicopter in a level attitude based on the type of helicopter and the landing gear
with the cyclic, and maintain heading with the antitorque installed.
pedals. Use the cyclic to direction of travel and ground track
identical (position 3). Allow the helicopter to descend gently 8. Failure to maintain proper rpm during and after
to the surface in a straight-a nd-level attitude, cushioning the touchdown.
landing with the collective. After surface contact, move the
cyclic slightly forward to ensure clearance between the tail 9. Maintaining poor alignment with direction of travel
boom and the rotor disk. Use the cyclic to maintain the surface during touchdown.
track (position 4). A pilot normally holds the collective
stationary until the helic opter stops; however, to get more Slope Operations
braking action, lower the collective slightly.
Prior to conducting any slope operations, be thoroughly
Keep in mind that, due to the increased ground friction when familiar with the characteristics of dynamic rollover and
the collective is lowered or if the landing is being executed mast bumping, which are disc ussed in Chapter 12, Helicopter
to a rough or irregular surface, the helicopter may come to Emergencies. The approach to a slope is similar to the
an abrupt stop and the nose might pitch forward. Exercise approach to any other landing area. During slope operations,
caution not to correct this pitching movement with aft cyclic, make allowances for wind, barriers, and forced landing sites
which could result in the rotor making contact with the tail in case of engine failure. Since the slope may constitute
boom. An abrupt stop may also cause excessive transmission an obstruction to wind passage, anticipate turbulence and
movement resulting in the transmission contacting its mount. downdrafts.
During the landing, maintain normal rpm with the throttle
and directional control with the antitorque pedals. Slope Landing
A pilot usually lands a helicopter across the slope rather than
For wheeled helicopters, use the same technique except after with the slope. Landing with the helicopter facing down
landing, lower the collective, neutralize the controls, and the slope or downhill is not recommended because of the
apply the brakes, as necessary, to slow the helicopter. Do not possibility of striking the tail rotor on the surface.
use aft cyclic when bringing the helicopter to a stop.
Technique
Refer to Figure 10-6. At the termination of the approach, if
necessary, move the helicopter slowly toward the slope, being
careful not to turn the tail upslope. Position the helicopter
across the slope at a stabilized hover headed into the wind
over the intended landing spot (frame 1). Downward pressure
10-7
1234
Figure 10-6. Slope landing. This ensures adequate rpm for immediate takeoff in case
the helicopter starts sliding down the slope. Use antitorque
on the collective starts the helicopter descending. As the pedals as necessary throughout the landing for heading
upslope skid touches the ground, hesitate momentarily in a control. Before reducing the rpm, move the cyclic control as
level attitude, then apply slight lateral cyclic in the direction necess ary to check that the helicopter is firmly on the ground.
of the slope (frame 2). This holds the skid against the slope
while the pilot continues lowering the downslope skid with Common Errors
the collective. As the collective is lowered, continue to move
the cyclic toward the slope to maintain a fixed position (frame 1. Failing to consider wind effects during the approach
3) The slope must be shallow enough to hold the helicopter and landing.
against it with the cyclic during the entire landing. A slope
of 5° is considered maximum for normal operation of most 2. Failing to maintain proper rpm throughout the entire
helicopters. Consult the RFM or POH for the specific maneuver.
limitations of the helicopter being flown.
3. Failure to maintain heading resulting in a turning or
Be aware of any abnormal vibration or mast bumping that pivoting motion.
signals maximum cyclic deflection. If this occurs, abandon
the landing because the slope is too steep. In most helicopters 4. Turning the tail of the helicopter into the
with a counterclockwise rotor system, landings can be made slope.
on steeper slopes when holding the cyclic to the right. When
landing on slopes using left cyclic, some cyclic input must 5. Lowering the downslope skid or wheel too rapidly.
be used to overcome the translating tendency. If wind is not
a factor, consider the drifting tendency when determining 6. Applying excessive cyclic control into the slope,
landing direction. causing mast bumping.
After the downslope skid is on the surface, reduce the Slope Takeoff
collective to full down, and neutralize the cyclic and pedals A slope takeoff is basically the reverse of a slope landing.
(frame 4). Normal operating rpm should be maintained [Figure 10-7] Conditions that may be associated with the
until the full weight of the helicopter is on the landing gear. slope, such as turbulence and obstacles, must be considered
during the takeoff. Planning should include suitable forced
landing areas.
123
Figure 10-7. Slope takeoff.
10-8
Technique Confined Area Operations
Begin the takeoff by increasing rpm to the normal range with
the collective full down. Then, move the cyclic toward the A confined area is an area where the flight of the helicopter
slope (frame 1). Holding the cyclic toward the direction of is limited in some direction by terrain or the presence of
the slope causes the downslope skid to rise as the pilot slowly obstructions, natural or manmade. For example, a clearing
raises the collective (frame 2). As the skid comes up, move in the woods, a city street, a road, a building roof, etc., can
the cyclic as necessary to maintain a level attitude in relation each be regarded as a confined area. The helicopter pilot has
to the horizon. If properly coordinated, the helicopter should added responsibilities when conducting operations from a
attain a level attitude as the cyclic reaches the neutral position. confined area that airplanes pilots do not. He or she assumes
At the same time, use antitorque pedal pressure to maintain the additional roles of the surveyor, engineer, and manager
heading and throttle to maintain rpm. With the helicopter when selecting an area to conduct operations. While airplane
level and the cyclic centered, pause momentarily to verify pilots generally operate from known pre-surveyed and
everything is correct, and then gradually raise the collective improved landing areas, helicopter pilots fly into areas never
to complete the liftoff (frame 3). After reaching a hover, used before for helicopter operations. Generally, takeoffs and
avoid hitting the ground with the tail rotor by not turning the landings should be made into the wind to obtain maximum
helicopter tail upslope and gaining enough altitude to ensure airspeed with minimum groundspeed. The pilot should begin
the tail rotor is clear. If an upslope wind exists, execute a with as nearly accurate an altimeter setting as possible to
crosswind takeoff and then make a turn into the wind after determine the altitude.
clearing the ground with the tail rotor.
There are several things to consider when operating in
Common Errors confined areas. One of the most important is maintaining
a clearance between the rotors and obstacles forming the
1. Failing to adjust cyclic control to keep the helic opter confined area. The tail rotor deserves special consideration
from sliding down slope. because, in some helicopters, it is not always visible from
the cabin. This not only applies while making the approach,
2. Failing to maintain proper rpm. but also while hovering. Another consideration is that wires
are especially difficult to see; however, their supporting
3. Holding excessive cyclic into the slope as the down devices, such as poles or towers, serve as an indication of
slope skid is raised. their presence and approximate height. If any wind is present,
expect some turbulence. [Figure 10-8]
4. Failure to maintain heading, resulting in a turning or
pivoting motion.
5. Turning the tail of the helicopter into the slope during
takeoff.
WIND
Figure 10-8. If the wind velocity is 10 knots or greater, expect updrafts on the windward side and downdrafts on the lee side of obstacles.
Plan the approach with these factors in mind, but be ready to alter plans if the wind speed or direction changes.
10-9
Something else to consider is the availability of forced Takeoff
landing areas during the planned approach. Think about A confined area takeoff is considered an altitude over airspeed
the possibility of flying from one alternate landing area to maneuver where altitude gain is more important to airspeed
another throughout the approach, while avoiding unfavorable gain. Before takeoff, make a reconnaissance from the ground
areas. Always leave a way out in case the landing cannot be or cockpit to determine the type of takeoff to be performed,
completed or a go-around is necessary. to determine the point from which the takeo ff should be
initiated to ensure the maximum amount of available area,
During the high reconnaissance, the pilot needs to formulate and finally, how to maneuver the helicopter best from the
a takeoff plan as well. The heights of obstacles need to be landing point to the proposed takeo ff position.
determined. It is not good practice to land in an area and
then determine that insufficient power exists to depart. If wind conditions and available area permit, the heli
Generally, more power is required to take off than to land copter should be brought to a hover, turned around, and
so the takeoff criteria is most crucial. Fixing the departure hovered forward from the landing position to the takeoff
azimuth or heading on the compass is a good technique to position. Under certain conditions, sideward flight to the
use. This ensures that the pilot is able to take off over the takeoff position may be preferred, but rearward flight may
preselected departure path when it is not visible while sitting be necessary, stopping often while moving to check on the
in the confined area. location of obstacles relative to the tail rotor.
Approach When planning the takeoff, consider the direction of the
A high reconnaissance should be completed before initiating wind, obstructions, and forced landing areas. To help fly up
the confined area approach. Start the approach phase using and over an obstacle, form an imaginary line from a point
the wind and speed to the best possible advantage. Keep in on the leading edge of the helicopter to the highest obstacle
mind areas suitable for forced landing. It may be necessary to to be cleared. Fly this line of ascent with enough power
choose a crosswind approach that is over an open area, then to clear the obstacle by a safe distance. After clearing the
one directly into the wind that is over trees. If these conditions obstacle, maintain the power setting and accelerate to the
exist, consider the possibility of making the initial phase of normal climb speed. Then, reduce power to the normal climb
the approach crosswind over the open area and then turning power setting.
into the wind for the final portion of the approach.
Common Errors
Always operate the helicopter as close to its normal
capabilities as possible, taking into consideration the situation 1. Failure to perform, or improper performance of, a high
at hand. In all confined area operations, with the exception or low reconnaissance.
of the pinnacle operation, the angle of descent should be no
steeper than necessary to clear any barrier with the tail rotor 2. Approach angle that is too steep or too shallow for the
in the approach path and still land on the selected spot. The existing conditions.
angle of climb on takeoff should be normal, or not steeper
than necessary to clear any barrier. Clearing a barrier by a 3. Failing to maintain proper rpm.
few feet and maintaining normal operating rpm, with perhaps
a reserve of power, is better than clearing a barrier by a wide 4. Failure to consider emergency landing areas.
margin but with a dangerously low rpm and no power reserve.
5. Failure to select a specific landing spot.
Always make the landing to a specific point and not to some
general area. This point should be located well forward, 6. Failure to consider how wind and turbulence could
away from the approach end of the area. The more confined affect the approach.
the area is, the more essential it is that the helicopter land
precisely at a definite point. Keep this point in sight during 7. Improper takeoff and climb technique for existing
the entire final approach. conditions.
When flying a helicopter near obstacles, always consider 8. Failure to maintain safe clearance distance from
the tail rotor. A safe angle of descent over barriers must be obstructions.
established to ensure tail rotor clearance of all obstructions.
After coming to a hover, avoid turning the tail into obstructions. Pinnacle and Ridgeline Operations
A pinnacle is an area from which the surface drops away
steeply on all sides. A ridgeline is a long area from which
the surface drops away steeply on one or two sides, such
as a bluff or precipice. The absence of obstacles does not
10-10
necessarily decrease the difficulty of pinnacle or ridgeline On landing, take advantage of the long axis of the area when
operations. Updrafts, downdrafts, and turbulence, together wind conditions permit. Touchdown should be made in the
with unsuitable terrain in which to make a forced landing, forward portion of the area. When approaching to land on
may still present extreme hazards. pinnacles, especially manmade areas such as rooftop pads,
the pilot should determine the personnel access pathway to
Approach and Landing the helipad and ensure that the tail rotor is not allowed to
If there is a need to climb to a pinnacle or ridgeline, do it on intrude into that walkway or zone. Parking or landing with the
the upwind side, when practicable, to take advantage of any tail rotor off the platform ensures personnel safety. Always
updrafts. The approach flightpath should be parallel to the perform a stability check prior to reducing rpm to ensure
ridgeline and into the wind as much as possib le. [Figure 10-9] the landing gear is on firm terrain that can safely support
the weight of the helicopter. Accomplish this by slowly
moving the cyclic and pedals while lowering the collective.
If movement is detected, reposition the aircraft.
Figure 10-9. When flying an approach to a pinnacle or ridgeline, Takeoff
avoid the areas where downdrafts are present, especially when A pinnacle takeoff is considered an airspeed over altitude
excess power is limited. If downdrafts are encountered, it may maneuver which can be made from the ground or from a
become necessary to make an immediate turn away from the hover. Since pinnacles and ridgelines are generally higher
pinnacle to avoid being forced into the rising terrain. than the immediate surrounding terrain, gaining airspeed
on the takeoff is more important than gaining altitude. As
airspeed increases, the departure from the pinnacle is more
rapid and helicopter time in the “avoid” area of the height/
velocity decreases. [Figure 10-10] In addition to covering
unfavorable terrain rapidly, a higher airspeed affords a more
favorable glide angle and thus contributes to the chances
of reaching a safe area in the event of a forced landing.
If a suitable forced landing area is not available, a higher
airspeed also permits a more effective flare prior to making
an autorotative landing.
800
700
Load, altitude, wind conditions, and terrain features Height above ground (feet) 600
determine the angle to use in the final part of an approach. 500
As a general rule, the greater the winds are, the steeper the
approach needs to be to avoid turbulent air and downdrafts.
Groundspeed during the approach is more difficult to judge 400
because visual references are farther away than during
approaches over trees or flat terrain. Pilots must continually 300 Operation in shaded areas
perceive the apparent rate of closure by observing the apparent must be avoided
change in size of the landing zone features. Avoid the
appearance of an increasing rate of closure to the landing site. 200 8,500 lb gross weight
The apparent rate of closure should be that of a brisk walk. If and below
a crosswind exists, remain clear of down-drafts on the leeward
or downwind side of the ridgeline. If the wind velocity makes 100
the crosswind landing hazardous, it may be possible to make
a low, coordinated turn into the wind just prior to terminating 0
the approach. When making an approach to a pinnacle, avoid 0 10 20 30 40 50 60 70 80 90 100 110 120
leeward turbulence and keep the helicopter within reach of a Airspeed KIAS (knots)
forced landing area as long as possible.
Figure 10-10. Height/velocity chart.
10-11
On takeoff, as the helicopter moves out of ground effect,
maintain altitude and accelerate to normal climb airspeed.
When normal climb speed is attained, establish a normal
climb attitude. Never dive the helicopter down the slope after
clearing the pinnacle.
Common Errors
1. Failing to perform, or improper performance of, a high
or low reconnaissance.
2. Flying the approach angle too steep or too shallow for
the existing conditions.
3. Failing to maintain proper rpm.
4. Failing to consider emergency landing areas.
5. Failing to consider how wind and turbulence could
affect the approach and takeoff.
6. Failure to maintain pinnacle elevation after takeoff.
7. Failure to maintain proper approach rate of closure.
8. Failure to achieve climb airspeed in timely manner.
Chapter Summary
This chapter described advanced flight maneuvers such as
slope landings, confined area landings, and running takeoffs.
The correlation between helicopter power requirements, the
environment, and safety were also explained to familiarize
the pilot with how the helicopter reacts during different
maneuvers. Hazards associated with helicopter flight and
certain aerodynamic considerations were also discussed.
10-12
HChapeterl1i1copter Emergencies
and Hazards
Introduction
Today, helicopters are quite reliable. However, emergencies
do occur, whether a result of mechanical failure or pilot
error, and should be anticipated. Regardless of the cause, the
recovery needs to be quick and precise. By having a thorough
knowledge of the helicopter and its systems, a pilot is able
to handle the situation more readily. Helicopter emergencies
and the proper recovery procedures should be discussed and,
when possible, practiced in flight. In addition, by knowing
the conditions that can lead to an emergency, many potential
accidents can be avoided.
11-1
Autorotation Several factors affect the rate of descent in autorotation:
density altitude, gross weight, rotor rpm, and airspeed. The
In a helicopter, an autorotative descent is a power-off primary way to control the rate of descent is with airspeed.
maneuver in which the engine is disengaged from the main Higher or lower airspeed is obtained with the cyclic pitch
rotor system and the rotor blades are driven solely by the control just as in normal powered flight. In theory, a pilot
upward flow of air through the rotor. [Figure 11-1] In other has a choice in the angle of descent varying from a vertical
words, the engine is no longer supplying power to the main descent to maximum range, which is the minimum angle of
rotor. descent. Rate of descent is high at zero airspeed and decreases
to a minimum at approximately 50–60 knots, depending upon
The most common reason for an autorotation is failure of the the particular helicopter and the factors just mentioned. As
engine or drive line, but autorotation may also be performed the airspeed increases beyond that which gives minimum rate
in the event of a complete tail rotor failure, since there is of descent, the rate of descent increases again.
virtually no torque produced in an autorotation. In both
areas, maintenance has often been a contributing factor to the When landing from an autorotation, the only energy available
failure. Engine failures are also caused by fuel contamination to arrest the descent rate and ensure a soft landing is the
or exhaustion as well resulting in a forced autorotation. kinetic energy stored in the rotor blades. Tip weights can
greatly increase this stored energy. A greater amount of rotor
If the engine fails, the freewheeling unit automatically energy is required to stop a helicopter with a high rate of
disengages the engine from the main rotor allowing the descent than is required to stop a helicopter that is descending
main rotor to rotate freely. Essentially, the freewheeling unit more slowly. Therefore, autorotative descents at very low or
disengages anytime the engine revolutions per minute (rpm) very high airspeeds are more critical than those performed
is less than the rotor rpm. at the minimum rate of descent airspeed.
At the instant of engine failure, the main rotor blades are Each type of helicopter has a specific airspeed and rotor rpm
producing lift and thrust from their angle of attack (AOA) at which a power-off glide is most efficient. The specific
and velocity. By lowering the collective pitch, which must be airspeed is somewhat different for each type of helicopter, but
done immediately in case of an engine failure, lift and drag certain factors affect all configurations in the same manner. In
are reduced, and the helicopter begins an immediate descent, general, rotor rpm maintained in the low green area gives more
thus producing an upward flow of air through the rotor distance in an autorotation. Higher weights may require more
system. This upward flow of air through the rotor provides collective pitch to control rotor rpm. Some helicopters need slight
sufficient thrust to maintain rotor rpm throughout the descent. adjustments to minimum rotor rpm settings for winter versus
Since the tail rotor is driven by the main rotor transmission summer conditions, and high altitude versus sea level flights. For
during autorotation, heading control is maintained with the specific autorotation airspeeds and rotor rpm combinations for a
antitorque pedals as in normal flight. particular helicopter, refer to the Federal Aviation Administration
(FAA)-approved rotorcraft flight manual (RFM).
Normal Powered Flight Autorotation
Direction of flight
Direction of flight
Figure 11-1. During an autorotation, the upward flow of relative wind permits the main rotor blades to rotate at their normal speed. In
effect, the blades are “gliding” in their rotational plane.
11-2
The specific airspeed and rotor rpm for autorotation is minimal groundspeed. As proficiency increases, the amount
established for each type of helicopter on the basis of of ground run may be reduced.
average weather, wind conditions, and normal loading.
When the helicopter is operated with heavy loads in high Technique
density altitude or gusty wind conditions, best performance Refer to Figure 11-2 (position 1). From level flight at
is achieved from a slightly increased airspeed in the descent. the appropriate airspeed (cruise or the manufacturer’s
For autorotation at low density altitude and light loading, recommended airspeed), 500–700 feet above ground level
best performance is achieved from a slight decrease in (AGL), and heading into the wind, smoothly but firmly
normal airspeed. Following this general procedure of fitting lower the collective pitch control to the full down position,
airspeed and rotor rpm to existing conditions, a pilot can maintaining rotor rpm in the green arc with collective. If
achieve approximately the same glide angle in any set of the collective is in the full down position, the rotor rpm is
circumstances and estimate the touchdown point. then being controlled by the mechanical pitch stops. During
maintenance, the rotor stops must be set to allow minimum
Pilots should practice autorotations with varying airspeeds autorotational rpm with a light loading. This means that some
between the minimum rate of descent to the maximum glide collective pitch adjustment can be made if the air density or
angle airspeed. The decision to use the appropriate airspeed helicopter loading changes. After entering an autorotation,
for the conditions and availability of landing area must be collective pitch must be adjusted to maintain the desired
instinctive. The helicopter glide ratio is much less than that of rotor rpm.
a fixed wing aircraft and takes some getting used to. The flare
to land at 55 KIAS will be significantly different than the flare 1
from 80 KIAS. Rotor rpm control is critical at these points
to ensure adequate rotor energy for cushioning the landing.
Straight-In Autorotation 2
A straight-in autorotation implies an autorotation from 3
altitude with no turns. Winds have a great effect on an
autorotation. Strong headwinds cause the glide angle to be 4
steeper due to the slower groundspeed. For example, if the
helicopter is maintaining 60 knots indicated airspeed and the 5
wind speed is 15 knots, then the groundspeed is 45 knots. The
angle of descent will be much steeper, although the rate of Figure 11-2. Straight-in autorotation.
descent remains the same. The speed at touchdown and the
resulting ground run depend on the groundspeed and amount Coordinate the collective movement with proper antitorque
of deceleration. The greater the degree of deceleration, or pedal for trim, and apply cyclic control to maintain proper
flare, and the longer it is held, the slower the touchdown speed airspeed. Once the collective is fully lowered, decrease
and the shorter the ground run. Caution must be exercised throttle to ensure a clean split/separation of the needles. This
at this point as the tail rotor will be the closest component means that the rotor rpm is higher than the engine rpm and
of the helicopter to the ground. If timing is not correct and a a clear indication that the freewheeling unit has allowed the
landing attitude not set at the appropriate time, the tail rotor engine to disconnect. After splitting the needles, readjust
may contact the ground causing a forward pitching moment the throttle to keep engine rpm above normal idling speed,
of the nose and possible damage to the helicopter. but not high enough to cause rejoining of the needles. The
manufacturer often recommends the proper rpm for that
A headwind is a contributing factor in accomplishing a slow particular helicopter.
touchdown from an autorotative descent and reduces the
amount of deceleration required. The lower the speed desired At position 2, adjust attitude with cyclic control to obtain the
at touchdown is, the more accurate the timing and speed of manufacturer’s recommended autorotation or best gliding
the flare must be, especially in helicopters with low-inertia speed. Adjust collective pitch control, as necessary, to
rotor systems. If too much collective pitch is applied too maintain rotor rpm in the green arc. Aft cyclic movements
early during the final stages of the autorotation, the kinetic
energy may be depleted, resulting in little or no cushioning
effect available. This could result in a hard landing with
corresponding damage to the helicopter. It is generally better
practice to accept more ground run than a hard landing with
11-3
cause an increase in rotor rpm, which is then controlled by is required to maintain heading as collective pitch is raised
a small increase in collective pitch control. Avoid a large due to the reduction in rotor rpm and the resulting reduced
collective pitch increase, which results in a rapid decay of effect of the tail rotor. Touch down in a level flight attitude.
rotor rpm, and leads to “chasing the rpm.” Avoid looking
straight down in front of the aircraft. Continually crosscheck Control response with increased pitch angles will be slightly
attitude, trim, rotor rpm, and airspeed. different than normal. With a decrease in main rotor rpm,
the antitorque authority is reduced, requiring larger control
At the altitude recommended by the manufacturer (position inputs to maintain heading at touchdown.
3), begin the flare with aft cyclic control to reduce forward
airspeed and decrease the rate of descent. Maintain heading Some helicopters have a canted tail stabilizer like the
with the antitorque pedals. During the flare maintain rotor rpm Schweitzer 300. It is crucial that the student apply the
in the green range. Care must be taken in the execution of the appropriate pedal input at all times during the autorotation.
flare so that the cyclic control is neither moved rearward so If not the tailboom tends to swing to the right, which allows
abruptly that it causes the helicopter to climb nor moved so the canted stabilizer to raise the tail. This can result in a
slowly that it does not arrest the descent, which may allow severe nose tuck which is quickly corrected with right pedal
the helicopter to settle so rapidly that the tail rotor strikes application.
the ground. In most helicopters, the proper flare attitude is
noticeable by an apparent groundspeed of a slow run. When A power recovery can be made during training in lieu of a full
forward motion decreases to the desired groundspeed, which touchdown landing. Refer to the section on power recovery
is usually the lowest possible speed (position 4), move the for the correct technique. After the helicopter has come to a
cyclic control forward to place the helicopter in the proper complete stop after touchdown, lower the collective pitch to
attitude for landing. the full-down position. Do not try to stop the forward ground
run with aft cyclic, as the main rotor blades can strike the
In many light helicopters, the student pilot can sit in the pilot tail boom. Rather, by lowering the collective slightly during
seat while the instructor pulls down on the helicopter’s tail the ground run, more weight is placed on the undercarriage,
until the tail rotor guard or “stinger” touches the surface. slowing the helicopter.
This action gives the student an idea of airframe attitude to
avoid, because a pilot should never allow ground contact One common error is holding the helicopter off the surface
unless the helicopter is more nose low than that attitude. versus cushioning the helicopter on to the surface during an
Limiting the flare to that pitch attitude may result in slightly autorotation. Holding the helicopter in the air by using all of
faster touchdown speeds, but will eliminate the possibility the rotor rpm potential energy usually causes the helicopter to
of tail rotor impact on level surfaces. have a hard landing, which results in the blades flexing down
and contacting the tail boom. The rotor rpm should be used
The landing gear height at this time should be approximately to cushion the helicopter on to the surface for a controlled,
3–15 feet AGL, depending on the altitude recommended by smooth landing instead of allowing the helicopter to drop
the manufacturer. As the apparent groundspeed and altitude the last few inches.
decrease, the helicopter must be returned to a more level
attitude for touchdown by applying forward cyclic. Some Common Errors
helicopters can be landed on the heels in a slightly nose high
attitude to help decrease the forward groundspeed whereas 1. Not understanding the importance of an immediate
others must land skids or landing gear level to equally spread entry into autorotation upon powerplant or driveline
the landing loads to all of the landing gear. Extreme caution failure.
should be used to avoid an excessive nose high and tail low
attitude below 10 feet. The helicopter must be close to the 2. Failing to use sufficient antitorque pedal when power
landing attitude to keep the tail rotor from contacting the is reduced.
surface.
3. Lowering the nose too abruptly when power is
At this point, if a full touchdown landing is to be made, allow reduced, thus placing the helicopter in a dive.
the helicopter to descend vertically (position 5). Increase
collective pitch, as necessary, to arrest the descent and 4. Failing to maintain proper rotor rpm during the
cushion the landing. This collective application uses some descent.
of the potential energy in the rotor system to help slow the
descent rate of the helicopter. Additional antitorque pedal 5. Applying up-collective pitch at an excessive altitude,
resulting in a hard landing, loss of heading control,
and possible damage to the tail rotor and main rotor
blade stops.
11-4
6. Failing to level the helicopter or achieve the To initiate an autorotation in other than in a low hover, lower
manufacturers preferred landing attitude. the collective pitch control. This holds true whether performing
a practice autorotation or in the event of an in-flight engine
7. Failure to maintain ground track in the air and keeping failure. This reduces the pitch of the main rotor blades and
the landing gear aligned with the direction of travel allows them to continue turning at normal rpm. During practice
during touchdown and ground contact. autorotations, maintain the rpm in the green arc with the throttle
while lowering collective. Once the collective is fully lowered,
8. Failure to minimize or eliminate lateral movement reduce engine rpm by decreasing the throttle. This causes a
during ground contact. split of the engine and rotor rpm needles.
9. Failure to go around if not within limits and specified Technique
criteria for safe autorotation. The most common types of autorotation are 90° and 180°
autorotations. For a 180° autorotation, establish the aircraft
Autorotation With Turns on the downwind at recommended airspeed and 500–700
A turn, or a series of turns, can be made during an autorotation feet AGL, parallel to the touchdown area. In a no-wind or
in order to land into the wind or avoid obstacles. The turn is headwind condition, establish the ground track approximately
usually made early so that the remainder of the autorotation 200 feet away from the touchdown point. If a strong
is the same as a straight-in autorotation. Making turns during crosswind exists, it is necessary to move the downwind leg
an autorotation generally uses cyclic control only. Use of closer or farther out. When abeam the intended touchdown
antitorque pedals to assist or increase the speed of the turn point, smoothly but firmly lower the collective pitch control
causes loss of airspeed and downward pitching of the nose. to the full down position, maintaining rotor rpm in the green
When an autorotation is initiated, sufficient antitorque pedal arc with collective.
pressure should be used to maintain the helicopter in trim
and prevent yawing. This pressure should not be changed Coordinate the collective movement with proper antitorque
to assist the turn. If the helicopter is flown out of trim in pedal for trim, and apply cyclic control to maintain proper
forward flight, the helicopter will be in either a slip or a skid attitude. Once the collective is fully lowered, decrease throttle
and airframe drag will be greatly increased which in turn to ensure a clean split/separation of the needles. After splitting
increases the rate of descent. Therefore, for the minimum the needles, readjust the throttle to keep engine rpm above
descent vertical speed, the trim ball should remain centered. normal idling speed, but not high enough to cause rejoining of
the needles. The manufacturer often recommends the proper
Use collective pitch control to manage rotor rpm. If rotor rpm rpm for that particular helicopter. Crosscheck attitude, trim,
builds too high during an autorotation, raise the collective rotor rpm, and airspeed.
sufficiently to decrease rpm back to the normal operating
range, then reduce the collective to maintain proper rotor rpm. After the descent and airspeed are established, roll into
If the collective increase is held too long, the rotor rpm may the turn. The turn should be approximately 180°, winds
decay rapidly. The pilot must then lower the collective and may cause the actual turn to be more or less than 180°. For
begin chasing the rotor rpm. If the rpm begins decreasing, training purposes, initially roll into a bank of a least 30°,
the pilot must again lower the collective. Always keep the but no more than 50°– 60°. Continuously check airspeed,
rotor rpm within the established range for the helicopter being rotor rpm, and trim throughout the turn. It is important to
flown. During a turn, rotor rpm increases due to the increased maintain the proper airspeed and to keep the aircraft in trim.
G loading, which induces a greater airflow through the rotor Changes in the aircraft’s attitude and the angle of bank cause
system. The rpm builds rapidly and can easily exceed the a corresponding change in rotor rpm. Adjust the collective, as
maximum limit if not controlled by use of collective. The necessary, in the turn to maintain rotor rpm in the green arc.
tighter the turn is and the heavier the gross weight is, the
higher the rpm is.
Cyclic input has a great effect on the rotor rpm. An aft cyclic At the 90° point, check the progress of the turn by glancing
input loads the rotor, resulting in coning and an increase in toward the landing area. Plan the second 90 degrees of turn
rotor rpm. A forward cyclic input unloads the rotor, resulting to roll out on the centerline. If the helicopter is too close,
in a decrease in rotor rpm. Therefore, it is prudent to attain decrease the bank angle; if too far out, increase the bank
the proper pitch attitude needed to ensure that the desired angle. Adjusting the bank angle will change the G loading,
landing area can be reached as soon as possible, and to make which in turn alters the airflow and results in rotor rpm
minor adjustments from there. changes. Keep the helicopter in trim with antitorque pedals.
11-5
The turn should be completed and the helicopter aligned with flight setting at the beginning of the flare. As the rotor system
the intended touchdown area prior to passing through 100 begins to dissipate its energy, the engine is up to speed as
feet AGL. If the collective pitch was temporarily increased the needles join when the rotor decreases into the normal
to control the rpm, it may need to be lowered on rollout to flight rpm.
prevent decay in rpm. Make an immediate power recovery
if the aircraft is not aligned with the touchdown point, and Helicopters that do not have the throttle control located on the
if the rotor rpm and/or airspeed are not within proper limits. collective require some additional prudence. The autorotation
Otherwise, complete the procedure as if it were a straight-in should be initiated with the power levers left in the “flight,”
autorotation. or normal, position. If a full touchdown is to be practiced, it
is common technique to move the power levers to the idle
Common Errors position once the landing area can safely be reached. In most
helicopters, the pilot is fully committed at that point to make
1. Failure to maintain trim during the turn (increases rate a power-off landing. However, it may be possible to make
of descent). a power recovery prior to passing through 100 feet AGL if
the powerplant can recover within that time period and the
2. Failure to maintain autorotation airspeed. instructor is very proficient. The pilot should comply with
the RFM instructions in all cases.
3. Failure to hold proper pitch attitude for type helicopter
(too high or too low). When practicing autorotations to a power recovery, the
differences between reciprocating engines and turbines
4. Failure to have proper alignment with touchdown zone may be profound. The reciprocating powerplant generally
by 100 feet AGL. responds very quickly to power changes, especially power
increases. Some turbines have delay times depending on
5. Failure to maintain rotor rpm within limits during the the type of fuel control or governing system installed. Any
maneuver. reciprocating engine needing turbocharged boost to develop
rated horse power may have significant delays to demands
6. Failure to go around if not within limits and specified for increased power, such as in the power recovery. Power
criteria for safe autorotation. recovery in those helicopters with slower engine response
times must have the engines begin to develop enough power
Practice Autorotation With a Power Recovery to rejoin the needles by approximately 100 feet AGL.
A power recovery is used to terminate practice autorotations
at a point prior to actual touchdown. After the power If a go-around is to be made, the cyclic control should be
recovery, a landing can be made or a go-around initiated. moved forward to resume forward flight. In transition from
a practice autorotation to a go-around, exercise caution to
Technique avoid an altitude-airspeed combination that would place the
At approximately 3–15 feet landing gear height AGL, helicopter in an unsafe area of its height-velocity diagram.
depending upon the helicopter being used, begin to level the
helicopter with forward cyclic control. Avoid excessive nose- This is one of the most difficult maneuvers to perform due to
high, tail-low attitude below 10 feet. Just prior to achieving the concentration needed when transitioning from powered
level attitude, with the nose still slightly up, coordinate flight to autorotation and then back again to powered flight.
upward collective pitch control with an increase in the For helicopters equipped with the power control on the
throttle to join the needles at operating rpm. The throttle and collective, engine power must be brought from flight power
collective pitch must be coordinated properly. to idle power and then back to a flight power setting. A delay
during any of these transitions can seriously affect rotor rpm
If the throttle is increased too fast or too much, an engine placing the helicopter in a situation that cannot be recovered.
overspeed can occur; if throttle is increased too slowly or
too little in proportion to the increase in collective pitch, a The cyclic must be adjusted to maintain the required
loss of rotor rpm results. Use sufficient collective pitch to airspeed without power, and then used for the deceleration
stop the descent, but keep in mind that the collective pitch flare, followed by the transition to level hovering flight.
application must be gradual to allow for engine response. Additionally, the cyclic must be adjusted to remove the
Coordinate proper antitorque pedal pressure to maintain compensation for translating tendency. The tail rotor is
heading. When a landing is to be made following the power no longer needed to produce antitorque thrust until almost
recovery, bring the helicopter to a hover at hovering altitude
and then descend to a landing.
When practicing autorotations with power recovery in nearly
all helicopters, the throttle or power levers should be at the
11-6
maximum power is applied to the rotor system for hovering necessary to keep the helicopter from drifting to the left, to
flight, when the tail rotor must again compensate for the main compensate for the loss of tail rotor thrust. However, use
rotor torque, which also demands compensation for the tail cyclic control, as required, to ensure a vertical descent and
rotor thrust and translating tendency. a level attitude. Do not adjust the collective pitch on entry.
The pedals must be adjusted from a powered flight anti- Helicopters with low inertia rotor systems settle immediately.
torque trim setting to the opposite trim setting to compensate Keep a level attitude and ensure a vertical descent with
for transmission drag and any unneeded vertical fin thrust cyclic control while maintaining heading with the pedals.
countering the now nonexistent torque and then reset to Any lateral movement must be avoided to prevent dynamic
compensate for the high power required for hovering flight. rollover. As rotor rpm decays, cyclic response decreases,
so compensation for winds will change, requiring more
All of the above must be accomplished during the 23 seconds cyclic input. At approximately 1 foot AGL, apply upward
of the autorotation and the tedious control inputs must be collective pitch control, as necessary, to slow the descent
made in the last 5 seconds of the maneuver. and cushion the landing without arresting the rate of descent
above the surface. Usually, the full amount of collective pitch
Common Errors is required just as the landing gear touches the surface. As
upward collective pitch control is applied, the throttle must
1. Initiating recovery too late, which requires a rapid be held in the idle detent position to prevent the engine from
application of controls and results in overcontrolling. re-engaging.
2. Failure to obtain and maintain a level attitude near the Helicopters with high inertia rotor systems settle more slowly
surface. after the throttle is closed. When the helicopter has settled
to approximately 1 foot AGL, apply upward collective pitch
3. Failure to coordinate throttle and collective pitch control while holding the throttle in the idle detent position
properly, which results in either an engine overspeed to slow the descent and cushion the landing. The timing of
or a loss of rotor rpm. collective pitch control application and the rate at which it is
applied depend upon the particular helicopter being used, its
4. Failure to coordinate proper antitorque pedal with the gross weight, and the existing atmospheric conditions. Cyclic
increase in power. control is used to maintain a level attitude and to ensure a
vertical descent. Maintain heading with antitorque pedals.
5. Late engine power engagement causing excessive
temperatures or torques, or rpm droop. When the weight of the helicopter is entirely resting on
the landing gear, cease application of upward collective.
6. Failure to go around if not within limits and specified When the helicopter has come to a complete stop, lower the
criteria for safe autorotation. collective pitch to the full-down position.
Power Failure in a Hover The timing of the collective pitch is a most important
Power failure in a hover, also called hovering autorotation, is consideration. If it is applied too soon, the remaining rpm
practiced so that a pilot can automatically make the correct may not be sufficient to make a soft landing. On the other
response when confronted with engine stoppage or certain hand, if collective pitch control is applied too late, surface
other emergencies while hovering. The techniques discussed contact may be made before sufficient blade pitch is available
in this section are for helicopters with a counterclockwise to cushion the landing. The collective must not be used to
rotor system and an antitorque rotor. hold the helicopter off the surface, causing a blade stall. Low
rotor rpm and ensuing blade stall can result in a total loss
Technique of rotor lift allowing the helicopter to fall to the surface and
To practice hovering autorotation, establish a normal possibly resulting in blade strikes to the tail boom and other
hovering altitude (approximately 2–3 feet) for the particular airframe damage such as landing gear damage, transmission
helicopter being used, considering load and atmospheric mount deformation, and fuselage cracking.
conditions. Keep the helicopter headed into the wind and
hold maximum allowable rpm. Common Errors
To simulate a power failure, firmly roll the throttle to the 1. Failure to use sufficient proper antitorque pedal when
engine idle position. This disengages the driving force of the power is reduced.
engine from the rotor, thus eliminating torque effect. As the
throttle is closed, apply proper antitorque pedal to maintain
heading. Usually, a slight amount of right cyclic control is
11-7
2. Failure to stop all sideward or backward movementHeight above surface (feet)In the simplest explanation, the H/V curve is a diagram in
prior to touchdown. which the shaded areas should be avoided, as the pilot may be
unable to complete an autorotation landing without damage.
3. Failure to apply up-collective pitch properly, resulting The H/V curve usually contains a takeoff profile, where the
in a hard touchdown. diagram can be traversed from 0 height and 0 speed to cruise,
without entering the shaded areas or with minimum exposure
4. Failure to touch down in a level attitude. to shaded areas.
5. Failure to roll the throttle completely to idle.
6. Failure to hover at a safe altitude for the helicopter The portion in the upper left of this diagram demonstrates
a flight profile that probably does not allow the pilot to
type, atmospheric conditions, and the level of training/ complete an autorotation successfully, primarily due to
proficiency of the pilot. having insufficient airspeed to enter an autorotative profile
7. Failure to go around if not within limits and specified in time to avoid a crash. The shaded area on the lower right
criteria for safe autorotation. is dangerous due to the airspeed and proximity to the ground
resulting in dramatically reduced reaction time for the pilot in
Height/Velocity Diagram the case of mechanical failure, or other in-flight emergencies.
This shaded area at the lower right is not portrayed in H/V
The height/velocity diagram or H/V curve is a graph charting curves for multi-engine helicopters capable of safely hovering
the safe/unsafe flight profiles relevant to a specific helicopter. and flying with a single engine failure.
As operation outside the safe area of the chart can be fatal
in the event of a power or driveline failure, it is sometimes The following examples further illustrate the relevance of
referred to as the dead man’s curve by helicopter pilots. By the H/V curve to a single-engine helicopter.
carefully studying the height/velocity diagram, a pilot is
able to avoid the combinations of altitude and airspeed that At low heights with low airspeed, such as a hover taxi, the
may not allow sufficient time or altitude to enter a stabilized pilot can simply use the potential energy from the rotor
autorotative descent. A pilot may want to refer to this diagram system to cushion the landing with collective, converting
during the remainder of the discussion on the height/velocity rotational inertia to lift. The aircraft is in a safe part of the
diagram. [Figure 11-3] H/V curve. At the extreme end of the scale (e.g., a three-
foot hover taxi at walking pace) even a complete failure to
500 recognize the power loss resulting in an uncushioned landing
would probably be survivable.
450
As the airspeed increases without an increase in height,
400 Avoid operation in shaded areas there comes a point at which the pilot’s reaction time would
be insufficient to react with a flare in time to prevent a high
350 speed, and thus probably fatal, ground impact. Another thing
Smooth hard surface to consider is the length of the tailboom and the response
time of the helicopter flight controls at slow airspeeds and
300 low altitudes. Even small increases in height give the pilot
much greater time to react; therefore, the bottom right part
250 of the H/V curve is usually a shallow gradient. If airspeed is
above ideal autorotation speed, the pilot’s instinct is usually
200 A to flare to convert speed to height and increase rotor rpm
through coning, which also immediately gets them out of
150 the dead man’s curve.
100
50 B Conversely, an increase in height without a corresponding
0 0 10 20 30 40 50 60 70 80 90 100 increase in airspeed puts the aircraft above a survivable
Indicated airspeed (knots) uncushioned impact height, and eventually above a height
(corrected for instrument error) where rotor inertia can be converted to sufficient lift to enable
a survivable landing. This occurs abruptly with airspeeds
Figure 11-3. Height/velocity diagram. much below the ideal autorotative speed (typically 40–80
knots). The pilot must have enough time to accelerate to
11-8
autorotation speed in order to autorotate successfully; this provide a restriction to gross weight, but to be an advisory of
directly relates to a requirement for height. Above a certain the autorotative capability of the helicopter during takeoff and
height the pilot can achieve autorotation speed even from a climb. A pilot must realize, however, that at gross weights
0 knot start, thus putting high OGE hovers outside the curve. above those recommended by the gross weight versus density
altitude chart, the values are unknown.
The typical safe takeoff profile involves initiation of forward
flight from a 2–3 feet landing gear height, only gaining Assuming a density altitude of 5,500 feet, the height/velocity
altitude as the helicopter accelerates through translational lift diagram in Figure 11-3 would be valid up to a gross weight
and airspeed approaches a safe autorotative speed. At this of approximately 1,700 pounds. This is found by entering
point, some of the increased thrust available may be used to the graph in Figure 11-4 at a density altitude of 5,500 feet
attain safe climb airspeed and will keep the helicopter out of (point A), then moving horizontally to the solid line (point
the shaded or hatched areas of the H/V diagram. Although B). Moving vertically to the bottom of the graph (point C),
helicopters are not restricted from conducting maneuvers with the existing density altitude, the maximum gross weight
that will place them in the shaded area of the H/V chart, it under which the height/velocity diagram is applicable is
is important for pilots to understand that operation in those 1,700 pounds.
shaded areas exposes pilot, aircraft, and passengers to a
certain hazard should the engine or driveline malfunction. Charts and diagrams for helicopters set out in Title 14 of the
The pilot should always evaluate the risk of the maneuver Code of Federal Regulations (14 CFR) Part 27, Airworthiness
versus the operational value. Standards: Normal Category Rotorcraft, are advisory in nature
and not regulatory. However, these charts do establish the safe
The Effect of Weight Versus Density Altitude parameters for operation. It is important to remember these
The height/velocity diagram [Figure 11-3] depicts altitude guidelines establish the tested capabilities of the helicopter.
and airspeed situations from which a successful autorotation Unless the pilot in command (PIC) is a certificated test pilot,
can be made. The time required, and therefore, altitude operating a helicopter beyond its established capabilities can
necessary to attain a steady state autorotative descent, is be considered careless and reckless operation, especially if
dependent on the weight of the helicopter and the density this action results is death or injury.
altitude. For this reason, the H/V diagram is valid only when
the helicopter is operated in accordance with the gross weight Common Errors
versus density altitude chart. If published, this chart is found
in the RFM for the particular helicopter. [Figure 11-4] The 1. Performing hovers higher than performed during
gross weight versus density altitude chart is not intended to training for hovering autorotations and practiced
proficiency.
7
2. Excessively nose-low takeoffs. The forward landing
Density altitude (thousands of feet) 6 B gear would impact before the pilot could assume a
landing attitude.
A
5 3. Adding too much power for takeoff.
4 4. Not maintaining landing gear aligned with takeoff
path until transitioning to a crab heading to account
3 C 2,000 for winds.
1,500 1,600 1,700 1,800 1,900
Settling With Power (Vortex Ring State)
Gross weight (pounds)
Vortex ring state describes an aerodynamic condition in
Figure 11-4. Gross weight versus density altitude. which a helicopter may be in a vertical descent with 20
percent up to maximum power applied, and little or no climb
performance. The term “settling with power” comes from
the fact that the helicopter keeps settling even though full
engine power is applied.
In a normal out-of-ground-effect (OGE) hover, the helicopter
is able to remain stationary by propelling a large mass of air
down through the main rotor. Some of the air is recirculated
near the tips of the blades, curling up from the bottom of the
11-9
rotor system and rejoining the air entering the rotor from The following combination of conditions is likely to cause
the top. This phenomenon is common to all airfoils and is settling in a vortex ring state in any helicopter:
known as tip vortices. Tip vortices generate drag and degrade
airfoil efficiency. As long as the tip vortices are small, their 1. A vertical or nearly vertical descent of at least 300
only effect is a small loss in rotor efficiency. However, when fpm. (Actual critical rate depends on the gross weight,
the helicopter begins to descend vertically, it settles into its rpm, density altitude, and other pertinent factors.)
own downwash, which greatly enlarges the tip vortices. In
this vortex ring state, most of the power developed by the 2. The rotor system must be using some of the available
engine is wasted in circulating the air in a doughnut pattern engine power (20–100 percent).
around the rotor.
3. The horizontal velocity must be slower than effective
translational lift.
In addition, the helicopter may descend at a rate that exceeds Some of the situations that are conducive to a settling with
the normal downward induced-flow rate of the inner blade power condition are: any hover above ground effect altitude,
sections. As a result, the airflow of the inner blade sections is specifically attempting to hover OGE at altitudes above the
upward relative to the disk. This produces a secondary vortex hovering ceiling of the helicopter, attempting to hover OGE
ring in addition to the normal tip vortices. The secondary without maintaining precise altitude control, pinnacle or
vortex ring is generated about the point on the blade where the rooftop helipads when the wind is not aligned with the landing
airflow changes from up to down. The result is an unsteady direction, and downwind and steep power approaches in
turbulent flow over a large area of the disk. Rotor efficiency which airspeed is permitted to drop below 10 knots depending
is lost even though power is still being supplied from the on the type of helicopter.
engine. [Figure 11-5]
When recovering from a settling with power condition,
the pilot tends first to try to stop the descent by increasing
collective pitch. However, this only results in increasing
the stalled area of the rotor, thereby increasing the rate of
descent. Since inboard portions of the blades are stalled,
cyclic control may be limited. Recovery is accomplished
by increasing airspeed, and/or partially lowering collective
pitch. In many helicopters, lateral cyclic combined with
lateral tailrotor thrust will produce the quickest exit from the
hazard assuming that there are no barriers in that direction.
In a fully developed vortex ring state, the only recovery may
be to enter autorotation to break the vortex ring state.
Tandem rotor helicopters should maneuver laterally to
achieve clean air in both rotors at the same time.
Figure 11-5. Vortex ring state. For settling with power demonstrations and training in
recognition of vortex ring state conditions, all maneuvers
A fully developed vortex ring state is characterized by an should be performed at an altitude of 2000–3000 feet AGL
unstable condition in which the helicopter experiences to allow sufficient altitude for entry and recovery.
uncommanded pitch and roll oscillations, has little or no
collective authority, and achieves a descent rate that may To enter the maneuver, come to an OGE hover, maintaining
approach 6,000 feet per minute (fpm) if allowed to develop. little or no airspeed (any direction), decrease collective
to begin a vertical descent, and as the turbulence begins,
A vortex ring state may be entered during any maneuver increase collective. Then allow the sink rate to increase to 300
that places the main rotor in a condition of descending in a fpm or more as the attitude is adjusted to obtain airspeed of
column of disturbed air and low forward airspeed. Airspeeds less than 10 knots. When the aircraft begins to shudder, the
that are below translational lift airspeeds are within this application of additional up collective increases the vibration
region of susceptibility to settling with power aerodynamics. and sink rate. As the power is increased, the rate of sink of
This condition is sometimes seen during quick-stop type the aircraft in the column of air will increase.
maneuvers or during recovery from autorotation.
11-10
If altitude is sufficient, some time can be spent in the Common Errors
vortices, to enable the pilot to develop a healthy knowledge
of the maneuver. However, helicopter pilots would normally 1. Failure to recognize the combination of contributing
initiate recovery at the first indication of settling with power. factors leading to retreating blade stall.
Recovery should be initiated at the first sign of vortex ring
state by applying forward cyclic to increase airspeed and/ or 2. Failure to compute VNE limits for altitudes to be flown.
simultaneously reducing collective. The recovery is complete
when the aircraft passes through effective translational lift Ground Resonance
and a normal climb is established.
Helicopters with articulating rotors (usually designs with
Common Errors three or more main rotor blades) are subject to ground
resonance, a destructive vibration phenomenon that occurs
1. Too much lateral speed for entry into settling with at certain rotor speeds when the helicopter is on the ground.
power. Ground resonance is a mechanical design issue that results
from the helicopter’s airframe having a natural frequency that
2. Excessive decrease of collective pitch. can be intensified by an out-of-balance rotor. The unbalanced
rotor system vibrates at the same frequency or multiple of the
Retreating Blade Stall airframe’s resonant frequency and the harmonic oscillation
increases because the engine is adding power to the system,
In forward flight, the relative airflow through the main rotor increasing the magnitude (or amplitude) of the vibrations
disk is different on the advancing and retreating side. The until the structure or structures fail. This condition can cause
relative airflow over the advancing side is higher due to the a helicopter to self-destruct in a matter of seconds.
forward speed of the helicopter, while the relative airflow on
the retreating side is lower. This dissymmetry of lift increases Hard contact with the ground on one corner (and usually
as forward speed increases. with wheel-type landing gear) can send a shockwave to the
main rotor head, resulting in the blades of a three-blade rotor
To generate the same amount of lift across the rotor disk, system moving from their normal 120° relationship to each
the advancing blade flaps up while the retreating blade flaps other. This movement occurs along the drag hinge and could
down. This causes the AOA to decrease on the advancing result in something like 122°, 122°, and 116° between blades.
blade, which reduces lift, and increase on the retreating blade, [Figure 11-6] When one of the other landing gear strikes the
which increases lift. At some point as the forward speed surface, the unbalanced condition could be further aggravated.
increases, the low blade speed on the retreating blade, and If the rpm is low, the only corrective action to stop ground
its high AOA cause a stall and loss of lift. resonance is to close the throttle immediately and fully lower
the collective to place the blades in low pitch. If the rpm is in
Retreating blade stall is a major factor in limiting a the normal operating range, fly the helicopter off the ground,
helicopter’s never-exceed speed (VNE) and its development
can be felt by a low frequency vibration, pitching up of the 122° 122°
nose, and a roll in the direction of the retreating blade. High
weight, low rotor rpm, high density altitude, turbulence and/ 116°
or steep, abrupt turns are all conducive to retreating blade
stall at high forward airspeeds. As altitude is increased, higher Figure 11-6. Ground resonance.
blade angles are required to maintain lift at a given airspeed.
Thus, retreating blade stall is encountered at a lower forward
airspeed at altitude. Most manufacturers publish charts and
graphs showing a VNE decrease with altitude.
When recovering from a retreating blade stall condition,
moving the cyclic aft only worsens the stall as aft cyclic
produces a flare effect, thus increasing the AOA. Pushing
forward on the cyclic also deepens the stall as the AOA on the
retreating blade is increased. Correct recovery from retreating
blade stall requires the collective to be lowered first, which
reduces blade angles and thus AOA. Aft cyclic can then be
used to slow the helicopter.
11-11
and allow the blades to rephase themselves automatically. force that rolls the helicopter over. When limited rotor blade
Then, make a normal touchdown. If a pilot lifts off and allows movement is coupled with the fact that most of a helicopter’s
the helicopter to firmly re-contact the surface before the weight is high in the airframe, another element of risk is added
blades are realigned, a second shock could move the blades to an already slightly unstable center of gravity. Pilots must
again and aggravate the already unbalanced condition. This remember that in order to remove thrust, the collective must
could lead to a violent, uncontrollable oscillation. be lowered as this is the only recovery technique available.
This situation does not occur in rigid or semi-rigid rotor Critical Conditions
systems because there is no drag hinge. In addition, skid-type Certain conditions reduce the critical rollover angle, thus
landing gear is not as prone to ground resonance as wheel- increasing the possibility for dynamic rollover and reducing
type landing gear since the rubber tires are not present and the chance for recovery. The rate of rolling motion is also
change the rebound characteristics. a consideration because, as the roll rate increases, there is
a reduction of the critical rollover angle at which recovery
Dynamic Rollover is still possible. Other critical conditions include operating
at high gross weights with thrust (lift) approximately equal
A helicopter is susceptible to a lateral rolling tendency, called to the weight.
dynamic rollover, when the helicopter is in contact with the
surface during takeoffs or landings. For dynamic rollover to Refer to Figure 11-7. The following conditions are most
occur, some factor must first cause the helicopter to roll or critical for helicopters with counterclockwise rotor rotation:
pivot around a skid or landing gear wheel, until its critical
rollover angle is reached. (5–8° depending on helicopter, 1. Right side skid or landing wheel down, since
winds, and loading) Then, beyond this point, main rotor translating tendency adds to the rollover force.
thrust continues the roll and recovery is impossible. After this
angle is achieved, the cyclic does not have sufficient range 2. Right lateral center of gravity (CG).
of control to eliminate the thrust component and convert it to
lift. If the critical rollover angle is exceeded, the helicopter 3. Crosswinds from the left.
rolls on its side regardless of the cyclic corrections made.
4. Left yaw inputs.
Dynamic rollover begins when the helicopter starts to pivot Main rotor thrust
laterally around its skid or wheel. This can occur for a variety
of reasons, including the failure to remove a tie down or Tail rotor thrust Tip-path plane neutral cyclic
skid-securing device, or if the skid or wheel contacts a fixed Tip-path plane full left cyclic
object while hovering sideward, or if the gear is stuck in
ice, soft asphalt, or mud. Dynamic rollover may also occur Crosswind
if you use an improper landing or takeoff technique or while
performing slope operations. Whatever the cause, if the gear Pivot point CG Bank
or skid becomes a pivot point, dynamic rollover is possible Weight angle
if not using the proper corrective technique.
Figure 11-7. Forces acting on a helicopter with right skid on the
Once started, dynamic rollover cannot be stopped by ground.
application of opposite cyclic control alone. For example,
the right skid contacts an object and becomes the pivot For helicopters with clockwise rotor rotation, the opposite
point while the helicopter starts rolling to the right. Even conditions would be true.
with full left cyclic applied, the main rotor thrust vector and
its moment follows the aircraft as it continues rolling to the
right. Quickly reducing collective pitch is the most effective
way to stop dynamic rollover from developing. Dynamic
rollover can occur with any type of landing gear and all types
of rotor systems.
It is important to remember rotor blades have a limited range
of movement. If the tilt or roll of the helicopter exceeds that
range (5–8°), the controls (cyclic) can no longer command a
vertical lift component and the thrust or lift becomes a lateral
11-12
Cyclic Trim Full opposite cyclic limit
When maneuvering with one skid or wheel on the ground, to prevent rolling motion
care must be taken to keep the helicopter cyclic control Tail rotor thrust
carefully adjusted. For example, if a slow takeoff is attempted
and the cyclic is not positioned and adjusted to account for Area of critical rollover Slope
translating tendency, the critical recovery angle may be Horizontal
exceeded in less than two seconds. Control can be maintained
if the pilot maintains proper cyclic position, and does not Figure 11-8. Upslope rolling motion.
allow the helicopter’s roll and pitch rates to become too
great. Fly the helicopter into the air smoothly while keeping seconds, may be adequate to stop the rolling motion. Take
movements of pitch, roll, and yaw small; do not allow any care, however, not to dump collective at an excessively
abrupt cyclic pressures. high rate, as this may cause a main rotor blade to strike the
fuselage. Additionally, if the helicopter is on a slope and the
Normal Takeoffs and Landings roll starts toward the upslope side, reducing collective too fast
Dynamic rollover is possible even during normal takeoffs may create a high roll rate in the opposite direction. When
and landings on relatively level ground, if one wheel or the upslope skid or wheel hits the ground, the dynamics of
skid is on the ground and thrust (lift) is approximately equal the motion can cause the helicopter to bounce off the upslope
to the weight of the helicopter. If the takeoff or landing is skid or wheel, and the inertia can cause the helicopter to roll
not performed properly, a roll rate could develop around about the downslope ground contact point and over on its
the wheel or skid that is on the ground. When taking off or side. [Figure 11-9]
landing, perform the maneuver smoothly and carefully adjust
the cyclic so that no pitch or roll movement rates build up, Full opposite cyclic limit
especially the roll rate. If the bank angle starts to increase to to prevent rolling motion
an angle of approximately 5–8°, and full corrective cyclic
does not reduce the angle, the collective should be reduced Tail rotor thrust
to diminish the unstable rolling condition. Excessive bank
angles can also be caused by landing gear caught in a tie Area of critical rollover
down strap, or a tie down strap still attached to one side of
the helicopter. Lateral loading imbalance (usually outside Slope
published limits) is another contributing factor.
Horizontal
Slope Takeoffs and Landings
During slope operations, excessive application of cyclic Figure 11-9. Downslope rolling motion.
control into the slope, together with excessive collective pitch
control, can result in the downslope skid or landing wheel Under normal conditions, the collective should not be pulled
rising sufficiently to exceed lateral cyclic control limits, and suddenly to get airborne because a large and abrupt rolling
an upslope rolling motion can occur. [Figure 11-8] moment in the opposite direction could occur. Excessive
application of collective can result in the upslope skid or
When performing slope takeoff and landing maneuvers, wheel rising sufficiently to exceed lateral cyclic control
follow the published procedures and keep the roll rates limits. This movement may be uncontrollable. If the
small. Slowly raise the downslope skid or wheel to bring the
helicopter level, and then lift off. During landing, first touch
down on the upslope skid or wheel, then slowly lower the
downslope skid or wheel using combined movements of cyclic
and collective. If the helicopter rolls approximately 5–8° to the
upslope side, decrease collective to correct the bank angle and
return to level attitude, then start the landing procedure again.
Use of Collective
The collective is more effective in controlling the rolling
motion than lateral cyclic, because it reduces the main rotor
thrust (lift). A smooth, moderate collective reduction, at a
rate of less than approximately full up to full down in two
11-13
helicopter develops a roll rate with one skid or wheel on the skid or wheel starts to leave the ground before the
ground, the helicopter can roll over on its side. downslope skid or wheel, smoothly and gently lower
the collective and check to see if the downslope skid or
Precautions wheel is caught on something. Under these conditions,
To help avoid dynamic rollover: vertical ascent is the only acceptable method of lift-off.
1. Always practice hovering autorotations into the wind, 12. Be aware that dynamic rollover can be experienced
and be wary when the wind is gusty or greater than 10 during flight operations on a floating platform if the
knots. platform is pitching/rolling while attempting to land
or takeoff. Generally, the pilot operating on floating
2. Use extreme caution when hovering close to fences, platforms (barges, ships, etc.) observes a cycle of
sprinklers, bushes, runway/taxi lights, tiedown cables, seven during which the waves increase and then
deck nets, or other obstacles that could catch a skid decrease to a minimum. It is that time of minimum
or wheel. Aircraft parked on hot asphalt over night wave motion that the pilot needs to use for the moment
might find the landing gear sunk in and stuck as the of landing or takeoff on floating platforms. Pilots
ramp cooled during the evening. operating from floating platforms should also exercise
great caution concerning cranes, masts, nearby boats
3. Always use a two-step lift-off. Pull in just enough (tugs) and nets.
collective pitch control to be light on the skids or
landing wheels and feel for equilibrium, then gently Low-G Conditions and Mast Bumping
lift the helicopter into the air.
Low acceleration of gravity (low-G or weightless) maneuvers
4. Hover high enough to have adequate skid or landing create specific hazards for helicopters, especially those with
wheel clearance with any obstacles when practicing semirigid main rotor systems because helicopters are primarily
hovering maneuvers close to the ground, especially designed to be suspended from the main rotor in normal flight
when practicing sideways or rearward flight. with only small variations for positive G load maneuvers.
Since a helicopter low-G maneuver departs from normal
5. Remember that when the wind is coming from flight conditions, it may allow the airframe to exceed the
the upslope direction, less lateral cyclic control is manufacturer’s design criteria. A low-G condition could have
available. disastrous results, the best way to prevent it from happening is
to avoid the conditions in which it might occur.
6. Avoid tailwind conditions when conducting slope
operations. Low-G conditions are not about the loss of thrust, rather the
imbalance of forces. Helicopters are mostly designed to have
7. Remember that less lateral cyclic control is available weight (gravity pulling down to the earth) and lift opposing
due to the translating tendency of the tail rotor when that force of gravity. Low-G maneuvers occur when this
the left skid or landing wheel is upslope. (This is true balance is disturbed. An example of this would be placing the
for counterclockwise rotor systems.) helicopter into a very steep dive. At the moment of pushover,
the lift and thrust of the rotor is forward, whereas gravity
8. Keep in mind that the lateral cyclic requirement is now vertical or straight down. Since the lift vector is no
changes when passengers or cargo are loaded or longer vertical and opposing the gravity (or weight) vector,
unloaded. the fuselage is now affected by the tail rotor thrust below the
plane of the main rotor. This tail rotor thrust moment tends to
9. Be aware that if the helicopter utilizes interconnecting make the helicopter fuselage tilt to the left. Pilots then apply
fuel lines that allow fuel to automatically transfer from right cyclic inputs to try to correct for the left. Since the main
one side of the helicopter to the other, the gravitational rotor system does not fully support the fuselage at this point,
flow of fuel to the downslope tank could change the the fuselage continues to roll and the pilot applies more right
CG, resulting in a different amount of cyclic control cyclic until the rotor system strikes the mast (mast bumping),
application to obtain the same lateral result. often ending with unnecessary fatal results. In mast bumping,
the rotor blade exceeds its flapping limits, causing the main
10. Do not allow the cyclic limits to be reached. If the rotor hub to “bump” into the rotor shaft. [Figure 11-10] The
cyclic control limit is reached, further lowering of the main rotor hub’s contact with the mast usually becomes more
collective may cause mast bumping. If this occurs, violent with each successive flapping motion. This creates a
return to a hover and select a landing point with a greater flapping displacement and leads to structural failure of
lesser degree of slope.
11. During a takeoff from a slope, begin by leveling the
main rotor disk with the horizon or very slightly into
the slope to ensure vertical lift and only enough lateral
thrust to prevent sliding on the slope. If the upslope
11-14
point, airflow will provide no any lift or driving force for
the system, and the result is disastrous.
Even though there is a safety factor built into most
helicopters, any time rotor rpm falls below the green arc
and there is power, simultaneously add throttle and lower
the collective. If in forward flight, gently applying aft cyclic
causes more air flow through the rotor system and helps
increase rotor rpm. If without power, immediately lower the
collective and apply aft cyclic.
Figure 11-10. Result of improper corrective action in a low-G Recovery From Low Rotor RPM
condition.
Under certain conditions of high weight, high temperature,
the rotor shaft. Since the mast is hollow, the structural failure or high density altitude, a pilot may get into a low rotor rpm
manifests itself either as shaft failure with complete separation situation. Although the pilot is using maximum throttle, the
of the main rotor system from the helicopter or a severely rotor rpm is low and the lifting power of the main rotor blades
damaged rotor mast. is greatly diminished. In this situation, the main rotor blades
have an AOA that has created so much drag that engine power
In situations like the one described above, the helicopter pilot is not sufficient to maintain or attain normal operating rpm.
should first apply aft cyclic to bring the vectors into balance, When rotor rpm begins to decrease, it is essential to recover
with lift up and gravity down. Since helicopter blades carry and maintain it.
the helicopter and have limited motion attachment, care must
be given to those attachment limits. Helicopter pilots should As soon as a low rotor rpm condition is detected, apply
always adhere to the maneuvering limitations stated in the additional throttle if it is available. If there is no throttle
RFM. There may be more than one reason or design criteria available, lower the collective. The amount the collective
which limits the helicopters flight envelope. Heed all of the can be lowered depends on altitude. Rotor rpm is life! If
manufacturer’s limitations and advisory data. Failure to do so the engine rpm is too low, it cannot produce its rated power
could lead to dire, unintended consequences. for the conditions because power generation is defined at a
qualified rpm value. An rpm that is too low equals low power.
Low Rotor RPM and Blade Stall Main rotor rpm must be maintained.
As mentioned earlier, low rotor rpm during an autorotation When operating at altitude, the collective may need to be
might result in a less than successful maneuver. However, lowered only once to regain rotor speed. If power is available,
if rotor rpm decays to the point at which all the rotor blades throttle can be added and the collective raised. Once
stall, the result is usually fatal, especially when it occurs at helicopter rotor blades cone excessively due to low rotor rpm,
altitude. It can occur in a number of ways, such as simply return the helicopter to the surface to allow the main rotor
rolling the throttle the wrong way, pulling more collective rpm to recover. Maintain precise landing gear alignment with
pitch than power available, or when operating at a high the direction of travel in case a landing is necessary. Low
density altitude. inertia rotor systems can become unrecoverable in 2 seconds
or less if the rpm is not regained immediately.
When the rotor rpm decreases, the blades produce less lift Since the tail rotor is geared to the main rotor, low main rotor
so the pilot feels it necessary to increase collective pitch to rpm may prevent the tail rotor from producing enough thrust
stop the descent or increase the climb. As the pitch increases, to maintain directional control. If pedal control is lost and the
drag increases, which requires more power to keep the altitude is low enough that a landing can be accomplished
blades turning at the proper rpm. When power is no longer before the turning rate increases dangerously, slowly decrease
available to maintain rpm and, therefore, lift, the helicopter collective pitch, maintain a level attitude with cyclic control,
begins to descend. This changes the relative wind and further and land.
increases the AOA. At some point, the blades stall unless
rpm is restored. As main rotor RPM decays, centrifugal
force continues to lessen until the lift force overcomes the
centrifugal forces and folds or breaks the blades. At this
11-15
System Malfunctions The throttle or power lever on some helicopters is not located
on the collective and readily available. Faced with the loss
The reliability and dependability record of modern helicopters of antitorque, the pilot of these models may need to achieve
is very impressive. By following the manufacturer’s forward flight and let the vertical fin stop the yawing rotation.
recommendations regarding operating limits and procedures With speed and altitude the pilot will have the time to set
and periodic maintenance and inspections, most systems and up for an autorotative approach and set the power control
equipment failures can be eliminated. Most malfunctions or to idle or off as the situation dictates. At low altitudes, the
failures can be traced to some error on the part of the pilot; pilot may not be able to reduce the power setting and enter
therefore, most emergencies can be averted before they the autorotation before impact.
happen. An actual emergency is a rare occurrence.
A mechanical control failure limits or prevents control of tail
Antitorque System Failure rotor thrust and is usually caused by a stuck or broken control
Antitorque failure usually falls into one of two categories. rod or cable. While the tail rotor is still producing antitorque
One is failure of the power drive portion of the tail rotor thrust, it cannot be controlled by the pilot. The amount of
system resulting in a complete loss of antitorque. The other antitorque depends on the position at which the controls jam
category covers mechanical control failures prohibiting or fail. Once again, the techniques differ depending on the
the pilot from changing or controlling tail rotor thrust even amount of tail rotor thrust, but an autorotation is generally
though the tail rotor may still be providing antitorque thrust. not required.
Tail rotor drive system failures include driveshaft failures, The specific manufacturer’s procedures should always be
tail rotor gearbox failures, or a complete loss of the tail rotor followed. The following is a generalized description of
itself. In any of these cases, the loss of antitorque normally procedures when more specific procedures are not provided.
results in an immediate spinning of the helicopter’s nose.
The helicopter spins to the right in a counterclockwise rotor Landing—Stuck Left Pedal
system and to the left in a clockwise system. This discussion A stuck left pedal (high power setting), which might be
is for a helicopter with a counterclockwise rotor system. The experienced during takeoff or climb conditions, results in
severity of the spin is proportionate to the amount of power the left yaw of the helicopter nose when power is reduced.
being used and the airspeed. An antitorque failure with a high Rolling off the throttle and entering an autorotation only
power setting at a low airspeed results in a severe spinning makes matters worse. The landing profile for a stuck left
to the right. At low power settings and high airspeeds, the pedal is best described as a normal to steep approach angle to
spin is less severe. High airspeeds tend to streamline the arrive approximately 2–3 feet landing gear height above the
helicopter and keep it from spinning. intended landing area as translational lift is lost. The steeper
angle allows for a lower power setting during the approach
If a tail rotor failure occurs, power must be reduced in order to and ensures that the nose remains to the left.
reduce main rotor torque. The techniques differ depending on
whether the helicopter is in flight or in a hover, but ultimately Upon reaching the intended touchdown area and at the
require an autorotation. If a complete tail rotor failure occurs appropriate landing gear height, increase the collective
while hovering, enter a hovering autorotation by rolling off smoothly to align the nose with the landing direction and
the throttle. If the failure occurs in forward flight, enter a cushion the landing. A small amount of forward cyclic is
normal autorotation by lowering the collective and rolling helpful to stop the nose from continuing to the right and
off the throttle. If the helicopter has enough forward airspeed directs the aircraft forward and down to the surface. In certain
(close to cruising speed) when the failure occurs, and wind conditions, the nose of the helicopter may remain to the
depending on the helicopter design, the vertical stabilizer left with zero to near zero groundspeed above the intended
may provide enough directional control to allow the pilot to touchdown point. If the helicopter is not turning, simply lower
maneuver the helicopter to a more desirable landing sight. the helicopter to the surface. If the nose of the helicopter is
Applying slight cyclic control opposite the direction of yaw turning to the right and continues beyond the landing heading,
compensates for some of the yaw. This helps in directional roll the throttle toward flight idle the amount necessary to
control, but also increases drag. Care must be taken not to stop the turn while landing. If the helicopter is beginning to
lose too much forward airspeed because the streamlining turn left, the pilot should be able to make the landing prior
effect diminishes as airspeed is reduced. Also, more altitude is to the turn rate becoming excessive. However, if the turn rate
required to accelerate to the correct airspeed if an autorotation begins to increase prior to the landing, simply add power to
is entered at a low airspeed. make a go-around and return for another landing.
11-16
Landing—Stuck Neutral or Right Pedal consider the horsepower required to run the propeller. For
The landing profile for a stuck neutral or a stuck right pedal example, a Cessna 172P is equipped with a 160-horsepower
is a low-power approach terminating with a running or roll- (HP) engine. A Robinson R-44 with a comparably sized tail
on landing. The approach profile can best be described as a rotor is rated for a maximum of 245 HP. If you assume the
shallow to normal approach angle to arrive approximately tail rotor consumes 50 HP, only 195 HP remains to drive
2–3 feet landing gear height above the intended landing the main rotor. If the pilot were to apply enough collective
area with a minimum airspeed for directional control. The to require 215 HP from the engine, and enough left pedal to
minimum airspeed is one that keeps the nose from continuing require 50 HP for the tail rotor, the resulting engine overload
to yaw to the right. would lead to one of two outcomes: slow down (reduction
in rpm) or premature failure. In either outcome, antitorque
Upon reaching the intended touchdown area and at the would be insufficient and total lift might be less than needed
appropriate landing gear height, reduce the throttle as to remain airborne.
necessary to overcome the yaw effect if the nose of the
helicopter remains to the right of the landing heading. The Every helicopter design requires some type of antitorque
amount of throttle reduction will vary based on power applied system to counteract main rotor torque and prevent spinning
and winds. The higher the power setting used to cushion the once the helicopter lifts off the ground. A helicopter is heavy,
landing, the more the throttle reduction will be. A coordinated and the powerplant places a high demand on fuel. Weight
throttle reduction and increased collective will result in a very penalizes performance, but all helicopters must have an
smooth touchdown with some forward ground speed. If the antitorque system, which adds weight. Therefore, the tail
nose of the helicopter is to the left of the landing heading, rotor is certified for normal flight conditions. Environmental
a slight increase in collective or aft cyclic may be used to forces can overwhelm any aircraft, rendering the inherently
align the nose for touchdown. The decision to land or go unstable helicopter especially vulnerable.
around has to be made prior to any throttle reduction. Using
airspeeds slightly above translational lift may be helpful to As with any aerodynamic condition, it is very important
ensure that the nose does not continue yawing to the right. If for pilots to not only understand the definition of terms but
a go-around is required, increasing the collective too much or more importantly how and why they happen, how to avoid
too rapidly with airspeeds below translational lift may cause the situation and lastly, how to correct the condition once it
a rapid spinning to the right. is encountered. We must first understand the capabilities of
the aircraft or even better what it is not capable of doing. For
Once the helicopter has landed and is sliding/rolling to a example, if you were flying a helicopter with a maximum
stop, the heading can be controlled with a combination of gross weight of 5,200 lbs, would a pilot knowingly try to take
collective, cyclic and throttle. To turn the nose to the right, on fuel, baggage and passengers causing the weight to be
raise the collective or apply aft cyclic. The throttle may be 5,500 lbs? A wise professional pilot should not ever exceed
increased as well if it is not in the full open position. To turn the certificated maximum gross weight or performance flight
the nose to the left, lower the collective or apply forward weight for any aircraft. The manuals are written for safety
cyclic. The throttle may be decreased as well if it is not and reliability. The limitations and emergency procedures
already at flight idle. are stressed because lapses in procedures or exceeding
limitations can result in aircraft damage or human fatalities.
Loss of Tail Rotor Effectiveness (LTE) At the very least, exceeding limitations will increase the costs
Loss of tail rotor effectiveness (LTE) or an unanticipated of maintenance and ownership of any aircraft and especially
yaw is defined as an uncommanded, rapid yaw towards the helicopters.
advancing blade which does not subside of its own accord.
It can result in the loss of the aircraft if left unchecked. It is Overloaded parts will fail before their designed lifetime.
very important for pilots to understand that LTE is caused There are no extra parts in helicopters. The respect and
by an aerodynamic interaction between the main rotor and discipline pilots exercise for following flight manuals should
tail rotor and not caused from a mechanical failure. Some also be applied to understanding aerodynamic conditions.
helicopter types are more likely to encounter LTE due to the If flight envelopes are exceeded, the end results can be
normal certification thrust produced by having a tail rotor catastrophic.
that, although meeting certification standards, is not always
able to produce the additional thrust demanded by the pilot. LTE is an aerodynamic condition and is the result of a control
margin deficiency in the tail rotor. It can affect all single rotor
A helicopter is a collection of compromises. Compare the helicopters that utilize a tail rotor of some design. The design
size of an airplane propeller to that of a tail rotor. Then, of main and tail rotor blades and the tail boom assembly can
11-17
affect the characteristics and susceptibility of LTE but will not 6. The airflow relative to the helicopter;
nullify the phenomenon entirely. Translational lift is obtained
by any amount of clean air through the main rotor system. a. Worst case—relative wind within ±15° of the
Chapter 3 discusses translational lift with respect to the main 10 o’clock position, generating vortices that
rotor blade, explaining that the more clean air there is going can blow directly into the tail rotor. This is
through the rotor system, the more efficient it becomes. The dictated by the characteristics of the helicopters
same holds true for the tail rotor. As the tail rotor works in aerodynamics of tailboom position, tailrotor size
less turbulent air, it reaches a point of translational thrust. At and position relative to the main rotor and vertical
this point, the tail rotor becomes aerodynamically efficient stabilizer, size and shape. [Figure 11-11]
and the improved efficiency produces more antitorque thrust.
The pilot can determine when the tail rotor has reached b. Weathercock stability—tailwinds from 120° to
translational thrust. As more antitorque thrust is produced, 240° [Figure 11 -12], such as left crosswinds,
the nose of the helicopter yaws to the left (opposite direction causing high pilot workload.
of the tail rotor thrust), forcing the pilot to correct with right
pedal application (actually decreasing the left pedal). This, c. T a i l r o t o r v o r t e x r i n g s t a t e ( 2 1 0 ° t o
in turn, decreases the AOA in the tail rotor blades. Pilots 330°). [Figure 11-13] Winds within this region
should be aware of the characteristics of the helicopter they will result in the development of the vortex ring
fly and be particularly aware of the amount of tail rotor pedal state of the tail rotor.
typically required for different flight conditions.
315° 330° 360° 30°
LTE is a condition that occurs when the flow of air through a 0° 20 k
tail rotor is altered in some way, either by altering the angle Wind vortRe3ex ig0in0ot°enrfoefredinscke 15 knots
or speed at which the air passes through the rotating blades 285° 10 knots 60°
of the tail rotor system. An effective tail rotor relies on a nots
stable and relatively undisturbed airflow in order to provide
a steady and constant antitorque reaction as discussed in 270° 90°
the previous paragraph. The pitch and angle of attack of the 120°
individual blades will determine the thrust output of the tail 240°
rotor. A change to any of these alters the amount of thrust
generated. A pilot’s yaw pedal input affects a thrust reaction 210° 150°
from the tail rotor. Altering the amount of thrust delivered
for the same yaw input creates an imbalance. Taking this 180°
imbalance to the extreme will result in the loss of effective
control in the yawing plane, and LTE will occur.
This alteration of tail rotor thrust can be affected by numerous Figure 11-11. Main rotor disk vortex interference.
external factors. The main factors contributing to LTE are:
7. Combinations (a, b, c) of these factors in a particular
1. Airflow and downdraft generated by the main rotor situation can easily require more anti-torque than the
blades interfering with the airflow entering the tail helicopter can generate and in a particular environment
rotor assembly. LTE can be the result.
2. Main blade vortices developed at the main blade tips Certain flight activities lend themselves to being more at
entering the tail rotor. high risk to LTE than others. For example, power line and
pipeline patrol sectors, low speed aerial filming/photography
3. Turbulence and other natural phenomena affecting the as well as in the Police and Helicopter Emergency Medical
airflow surrounding the tail rotor. Services (EMS) environments can find themselves in low
and slow situations over geographical areas where the exact
4. A high power setting, hence large main rotor wind speed and direction are hard to determine.
pitch angle, induces considerable main rotor blade
downwash and hence more turbulence than when the
helicopter is in a low power condition.
5. A slow forward airspeed, typically at speeds where
translational lift and translational thrust are in the
process of change and airflow around the tail rotor
will vary in direction and speed.
11-18
360° 2. Winds from ±15º of the 10 o’clock position
0° and probably on around to 5 o’clock position
[Figure 11-11]
330° 15 knots 30°
17 k 3. Tailwinds that may alter the onset of translational
10 knots lift and translational thrust hence induce high power
270° 60° demands and demand more anti-torque (left pedal)
300° nots than the tail rotor can produce.
5 knots 90° 4. Low speed downwind turns.
240° 120° 5. Large changes of power at low airspeeds.
6. Low speed flight in the proximity of physical
obstructions that may alter a smooth airflow to both
the main rotor and tail rotor.
Regio n of Wind 150° sta Pilots who put themselves in situations where the combinations
bility above occur should know that they are likely to encounter
210° LTE. The key is to not put the helicopter in a compromising
possible weathercock condition but if it does happen being educated enough to
yaw 180° by recognize the onset of LTE and be prepared to quickly react
introduction to it before the helicopter cannot be controlled.
Figure 11-12. Weathercock stability. Early detection of LTE followed by the immediate flight
control application of corrective action; applying forward
rin g state 330° 360° 30° cyclic to regain airspeed, applying right pedal not left as
0° 17 k necessary to maintain rotor RPM and reducing the collective
v3o0 r0t°e x 15 knots thus reducing the high power demand on the tail rotor is the
60° key to a safe recovery. Pilots should always set themselves
10 knots nots up when conducting any maneuver to have enough height
and space available to recover in the event they encounter
rotor an aerodynamic situation such as LTE.
Wind to tail 5 knots 90° Understanding the aerodynamic phenomenon of LTE is by far
270° the most important factor, and the ability and option to either
go around if making an approach or pull out of a maneuver
due safely and re-plan, is always the safe option. Having the
ability to fly away from a situation and re-think the possible
rou2g40h°n e s s 120° options should always be part of a pilot's planning process in
all phases of flight. Unfortunately, there have been many pilots
of who have idled a good engine and fully functioning tail rotor
system and autorotated a perfectly airworthy helicopter to the
n 150° crash site because they misunderstood or misperceived both
the limitations of the helicopter and the aerodynamic situation.
210° Regio 180°
Figure 11-13. Tail rotor vortex ring state. Main Rotor Disk Interference (285–315°)
Refer to Figure 11-11. Winds at velocities of 10–30 knots
Unfortunately, the aerodynamic conditions that a helicopter from the left front cause the main rotor vortex to be blown
is susceptible to are not explainable in black and white terms. into the tail rotor by the relative wind. This main rotor
LTE is no exception. There are a number of contributing disk vortex causes the tail rotor to operate in an extremely
factors but what is more important to understanding LTE turbulent environment. During a right turn, the tail rotor
are taking the contributing factors and couple them with experiences a reduction of thrust as it comes into the area of
situations that should be avoided. Whenever possible, pilots the main rotor disk vortex. The reduction in tail rotor thrust
should learn to avoid the following combinations: comes from the airflow changes experienced at the tail rotor
as the main rotor disk vortex moves across the tail rotor disk.
1. Low and slow flight outside of ground effect.
11-19
The effect of the main rotor disk vortex initially increases the LTE at Altitude
AOA of the tail rotor blades, thus increasing tail rotor thrust. At higher altitudes where the air is thinner, tail rotor thrust
The increase in the AOA requires that right pedal pressure and efficiency are reduced. Because of the high density
be added to reduce tail rotor thrust in order to maintain the altitude, powerplants may be much slower to respond to
same rate of turn. As the main rotor vortex passes the tail power changes. When operating at high altitudes and high
rotor, the tail rotor AOA is reduced. The reduction in the gross weights, especially while hovering, the tail rotor thrust
AOA causes a reduction in thrust and right yaw acceleration may not be sufficient to maintain directional control, and
begins. This acceleration can be surprising, since previously LTE can occur. In this case, the hovering ceiling is limited
adding right pedal to maintain the right turn rate. This thrust by tail rotor thrust and not necessarily power available. In
reduction occurs suddenly, and if uncorrected, develops these conditions, gross weights need to be reduced and/
into an uncontrollable rapid rotation about the mast. When or operations need to be limited to lower density altitudes.
operating within this region, be aware that the reduction in This may not be noted as criteria on the performance charts.
tail rotor thrust can happen quite suddenly, and be prepared
to react quickly to counter this reduction with additional left Reducing the Onset of LTE
pedal input. To help reduce the onset of LTE, follow these steps:
Weathercock Stability (120–240°) 1. Maintain maximum power-on rotor rpm. If the main
In this region, the helicopter attempts to weathervane, rotor rpm is allowed to decrease, the antitorque thrust
or weathercock, its nose into the relative wind. available is decreased proportionally.
[Figure 11-12] Unless a resisting pedal input is made, the
helicopter starts a slow, uncommanded turn either to the right 2. Avoid tailwinds below airspeeds of 30 knots. If loss
or left, depending upon the wind direction. If the pilot allows of translational lift occurs, it results in an increased
a right yaw rate to develop and the tail of the helicopter moves power demand and additional antitorque pressures.
into this region, the yaw rate can accelerate rapidly. In order
to avoid the onset of LTE in this downwind condition, it is 3. Avoid OGE operations and high power demand
imperative to maintain positive control of the yaw rate and situations below airspeeds of 30 knots at low altitudes.
devote full attention to flying the helicopter.
4. Be especially aware of wind direction and velocity
Tail Rotor Vortex Ring State (210–330°) when hovering in winds of about 8–12 knots. A loss
of translational lift results in an unexpected high power
Winds within this region cause a tail rotor vortex ring state to demand and an increased antitorque requirement.
develop. [Figure 11-13] The result is a nonuniform, unsteady
flow into the tail rotor. The vortex ring state causes tail 5. Be aware that if a considerable amount of left pedal
rotor thrust variations, which result in yaw deviations. The is being maintained, a sufficient amount of left pedal
net effect of the unsteady flow is an oscillation of tail rotor may not be available to counteract an unanticipated
thrust. Rapid and continuous pedal movements are necessary right yaw.
to compensate for the rapid changes in tail rotor thrust when
hovering in a left crosswind. Maintaining a precise heading 6. Be alert to changing wind conditions, which may be
in this region is difficult, but this characteristic presents experienced when flying along ridge lines and around
no significant problem unless corrective action is delayed. buildings.
However, high pedal workload, lack of concentration, and
overcontrolling can lead to LTE. 7. Execute slow turns to the right which would limit
the effects of rotating inertia, and the loading on the
When the tail rotor thrust being generated is less than the tailrotor to control yawing would be decreased.
thrust required, the helicopter yaws to the right. When
hovering in left crosswinds, concentrate on smooth pedal Recovery Technique
coordination and do not allow an uncommanded right yaw to If a sudden unanticipated right yaw occurs, the following
develop. If a right yaw rate is allowed to build, the helicopter recovery technique should be performed. Apply forward
can rotate into the wind azimuth region where weathercock cyclic control to increase speed. If altitude permits, reduce
stability then accelerates the right turn rate. Pilot workload power. As recovery is affected, adjust controls for normal
during a tail rotor vortex ring state is high. Do not allow a forward flight. A recovery path must always be planned,
right yaw rate to increase. especially when terminating to an OGE hover and executed
immediately if an uncommanded yaw is evident.
11-20
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